diff --git a/CLAUDE.md b/CLAUDE.md
index ff6586c..207cc41 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -86,6 +86,27 @@ Speichert: color, stroke, fontFamily, fontSize, bold, italic, zoom
 
 ---
 
+## Phase 4 Block 1 ✅ (2026-04-09)
+
+PWA-Usability-Features:
+- 4.g Seite löschen in PWA (ajax /api/pages.php DELETE)
+- 4.h Notiz pro Seite (POST /api/pages.php {note})
+- 4.j PDF-Vorschau-Modal nach Finalize (api/pdf.php liefert Blob mit JWT)
+- 4.b Touch-Unterschrift (openSignatureModal → api/pages.php?action=signature)
+- 4.e Web Share Target API (manifest + share.html + SW-Interception in IDB)
+
+Neue API-Endpoints:
+- api/pages.php — DELETE/POST (note, rotation) + ?action=signature&bericht_id=
+- api/pdf.php — liefert Final-PDF oder on-the-fly Preview, JWT via Query-Param
+
+PWA neue Modals (alle in app.js):
+- openPageActionsModal — tap auf Report-Page-Thumb, Notiz + Löschen
+- openPdfModal — iframe mit Blob-URL + Download-Link
+- openSignatureModal — Touch-Canvas 2:1, Clear, Save als PNG
+- openHelpModal — komplette Anleitung (bereits in v4 gebaut)
+
+Service Worker v5 (Share Target), manifest.webmanifest mit share_target.
+
 ## Phase 2 — Mobile-Vorbereitung + API-Layer (geplant)
 - 2.1 Mobile-Upload-Token Tabelle + Cleanup-Cron
 - 2.2 QR-Upload Lite Modal im Editor
diff --git a/api/customers.php b/api/customers.php
new file mode 100644
index 0000000..81013d8
--- /dev/null
+++ b/api/customers.php
@@ -0,0 +1,147 @@
+<?php
+/* GET /api/customers.php            — Liste der Kunden mit letzten Berichten
+ * GET /api/customers.php?id=<soc_id> — Kunden-Detail: Stammdaten + Aufträge + Berichte
+ * GET /api/customers.php?q=<search>  — Filter per Name
+ */
+require_once __DIR__.'/_inc.php';
+
+api_authenticate();
+global $db, $user, $conf, $langs;
+
+require_once DOL_DOCUMENT_ROOT.'/societe/class/societe.class.php';
+
+$id = (int) ($_GET['id'] ?? 0);
+$q  = (string) ($_GET['q'] ?? '');
+
+/* ----- LISTE ----- */
+if (!$id) {
+    $where = "s.entity IN (".getEntity('societe').")";
+    if ($q !== '') {
+        $q_esc = $db->escape($q);
+        $where .= " AND (s.nom LIKE '%$q_esc%' OR s.code_client LIKE '%$q_esc%' OR s.town LIKE '%$q_esc%')";
+    }
+    // Standardmäßig nur Kunden (client=1 oder 3) — keine reinen Lieferanten
+    $where .= " AND (s.client = 1 OR s.client = 2 OR s.client = 3)";
+
+    $sql = "SELECT s.rowid, s.nom, s.code_client, s.zip, s.town, s.phone, s.email,"
+        ." (SELECT COUNT(*) FROM ".$db->prefix()."bericht b"
+        ."    INNER JOIN ".$db->prefix()."commande c ON c.rowid = b.fk_element AND b.element_type='order' AND c.fk_soc = s.rowid) AS b_order,"
+        ." (SELECT COUNT(*) FROM ".$db->prefix()."bericht b"
+        ."    INNER JOIN ".$db->prefix()."facture f ON f.rowid = b.fk_element AND b.element_type='invoice' AND f.fk_soc = s.rowid) AS b_invoice,"
+        ." (SELECT MAX(c2.date_commande) FROM ".$db->prefix()."commande c2 WHERE c2.fk_soc = s.rowid) AS last_order_date"
+        ." FROM ".$db->prefix()."societe s"
+        ." WHERE ".$where
+        ." ORDER BY last_order_date DESC, s.nom ASC"
+        ." LIMIT 200";
+    $r = $db->query($sql);
+    if (!$r) api_fail('DB-Fehler: '.$db->lasterror(), 500);
+    $out = array();
+    while ($o = $db->fetch_object($r)) {
+        $bericht_count = (int) $o->b_order + (int) $o->b_invoice;
+        $out[] = array(
+            'id' => (int) $o->rowid,
+            'name' => $o->nom,
+            'code' => $o->code_client,
+            'zip' => $o->zip,
+            'town' => $o->town,
+            'phone' => $o->phone,
+            'email' => $o->email,
+            'bericht_count' => $bericht_count,
+            'last_order_date' => $o->last_order_date ? $db->jdate($o->last_order_date) : null,
+        );
+    }
+    api_ok(array('customers' => $out, 'count' => count($out)));
+}
+
+/* ----- DETAIL eines Kunden ----- */
+$soc = new Societe($db);
+if ($soc->fetch($id) <= 0) api_fail('Kunde nicht gefunden', 404);
+
+// Aufträge des Kunden
+$orders = array();
+$ro = $db->query("SELECT c.rowid, c.ref, c.date_commande, c.fk_statut, c.total_ttc"
+    ." FROM ".$db->prefix()."commande c"
+    ." WHERE c.fk_soc = ".((int) $id)
+    ." AND c.entity IN (".getEntity('commande').")"
+    ." ORDER BY c.date_commande DESC, c.rowid DESC LIMIT 50");
+if ($ro) {
+    while ($o = $db->fetch_object($ro)) {
+        // Bericht-Count pro Auftrag
+        $rb = $db->query("SELECT COUNT(*) AS n FROM ".$db->prefix()."bericht WHERE element_type='order' AND fk_element = ".((int) $o->rowid));
+        $bc = ($rb && ($rbo = $db->fetch_object($rb))) ? (int) $rbo->n : 0;
+        $orders[] = array(
+            'id' => (int) $o->rowid,
+            'ref' => $o->ref,
+            'date' => $db->jdate($o->date_commande),
+            'status' => (int) $o->fk_statut,
+            'total' => (float) $o->total_ttc,
+            'bericht_count' => $bc,
+        );
+    }
+}
+
+// Rechnungen des Kunden
+$invoices = array();
+$ri = $db->query("SELECT f.rowid, f.ref, f.datef, f.fk_statut, f.total_ttc"
+    ." FROM ".$db->prefix()."facture f"
+    ." WHERE f.fk_soc = ".((int) $id)
+    ." AND f.entity IN (".getEntity('facture').")"
+    ." ORDER BY f.datef DESC, f.rowid DESC LIMIT 50");
+if ($ri) {
+    while ($f = $db->fetch_object($ri)) {
+        $invoices[] = array(
+            'id' => (int) $f->rowid,
+            'ref' => $f->ref,
+            'date' => $db->jdate($f->datef),
+            'status' => (int) $f->fk_statut,
+            'total' => (float) $f->total_ttc,
+        );
+    }
+}
+
+// Alle Berichte des Kunden (über Joins)
+$reports = array();
+$rr = $db->query(
+    "SELECT b.rowid, b.ref, b.titel, b.status, b.datec, b.element_type, c.ref AS parent_ref"
+    ." FROM ".$db->prefix()."bericht b"
+    ." INNER JOIN ".$db->prefix()."commande c ON c.rowid = b.fk_element"
+    ." WHERE b.element_type = 'order' AND c.fk_soc = ".((int) $id)
+    ." UNION "
+    ."SELECT b.rowid, b.ref, b.titel, b.status, b.datec, b.element_type, f.ref AS parent_ref"
+    ." FROM ".$db->prefix()."bericht b"
+    ." INNER JOIN ".$db->prefix()."facture f ON f.rowid = b.fk_element"
+    ." WHERE b.element_type = 'invoice' AND f.fk_soc = ".((int) $id)
+    ." ORDER BY datec DESC LIMIT 100"
+);
+if ($rr) {
+    while ($b = $db->fetch_object($rr)) {
+        $reports[] = array(
+            'id' => (int) $b->rowid,
+            'ref' => $b->ref,
+            'titel' => $b->titel,
+            'status' => (int) $b->status,
+            'datec' => $db->jdate($b->datec),
+            'element_type' => $b->element_type,
+            'parent_ref' => $b->parent_ref,
+        );
+    }
+}
+
+api_ok(array(
+    'customer' => array(
+        'id' => (int) $soc->id,
+        'name' => $soc->name,
+        'code' => $soc->code_client,
+        'address' => $soc->address,
+        'zip' => $soc->zip,
+        'town' => $soc->town,
+        'country' => $soc->country,
+        'phone' => $soc->phone,
+        'email' => $soc->email,
+        'siret' => $soc->idprof1 ?? '',
+        'vat' => $soc->tva_intra ?? '',
+    ),
+    'orders' => $orders,
+    'invoices' => $invoices,
+    'reports' => $reports,
+));
diff --git a/api/pages.php b/api/pages.php
index cd9ec79..1bf253f 100644
--- a/api/pages.php
+++ b/api/pages.php
@@ -26,15 +26,134 @@ if ($method === 'POST' && $action === 'signature') {
     $bericht = new Bericht($db);
     if ($bericht->fetch($bericht_id) <= 0) api_fail('Bericht nicht gefunden', 404);
 
+    // Parent-Objekt (Kunde) holen — wir brauchen den Kundennamen für die Metadaten
+    $parent = bericht_fetch_parent($db, $bericht->element_type, $bericht->fk_element);
+    $kundename = $parent && !empty($parent->thirdparty) ? ($parent->thirdparty->name ?? '') : '';
+    $parent_ref = $parent ? $parent->ref : '';
+
+    // Zusatz-Felder vom Client
+    $signer_name = trim((string) ($_POST['signer_name'] ?? ''));
+    $gps_lat = isset($_POST['gps_lat']) ? (float) $_POST['gps_lat'] : null;
+    $gps_lon = isset($_POST['gps_lon']) ? (float) $_POST['gps_lon'] : null;
+
     require_once DOL_DOCUMENT_ROOT.'/core/lib/files.lib.php';
     $workdir = DOL_DATA_ROOT.'/bericht/work/'.$bericht_id;
     if (!is_dir($workdir)) dol_mkdir($workdir);
 
+    // Hash-Verkettung: SHA256 über alle vorherigen Seiten-Quelldateien
+    $prev_pages = BerichtPage::fetchAllForBericht($db, $bericht_id);
+    $hash_ctx = hash_init('sha256');
+    hash_update($hash_ctx, 'bericht:'.$bericht_id.'|ref:'.$bericht->ref);
+    foreach ($prev_pages as $pp) {
+        $full_pp = bericht_resolve_data_path($pp->source_path);
+        if ($full_pp && file_exists($full_pp)) {
+            hash_update_file($hash_ctx, $full_pp);
+        }
+        hash_update($hash_ctx, '|order:'.$pp->page_order.'|note:'.($pp->note ?? ''));
+    }
+    $chain_hash = hash_final($hash_ctx);
+
+    // Rohe Unterschrift vom Upload
+    $raw_sig_png = file_get_contents($_FILES['file']['tmp_name']);
+    if (!$raw_sig_png) api_fail('Upload fehlgeschlagen', 500);
+    $sig_img = @imagecreatefromstring($raw_sig_png);
+    if (!$sig_img) api_fail('PNG ungültig');
+    $sig_w = imagesx($sig_img);
+    $sig_h = imagesy($sig_img);
+
+    // Composite-Canvas: Metadaten oben, Unterschrift in der Mitte, Footer mit Hash unten
+    $canvas_w = max($sig_w, 1200);
+    $header_h = 180;
+    $footer_h = 120;
+    $sig_area_h = 500;
+    $canvas_h = $header_h + $sig_area_h + $footer_h;
+    $canvas = imagecreatetruecolor($canvas_w, $canvas_h);
+
+    $white = imagecolorallocate($canvas, 255, 255, 255);
+    $black = imagecolorallocate($canvas, 0, 0, 0);
+    $grey  = imagecolorallocate($canvas, 120, 120, 120);
+    $line_grey = imagecolorallocate($canvas, 200, 200, 200);
+    $dark_blue = imagecolorallocate($canvas, 51, 122, 183);
+    imagefill($canvas, 0, 0, $white);
+
+    // Header-Box
+    imagefilledrectangle($canvas, 0, 0, $canvas_w, $header_h, imagecolorallocate($canvas, 245, 248, 252));
+    imagerectangle($canvas, 0, 0, $canvas_w - 1, $header_h, $line_grey);
+
+    // Überschrift
+    $title = 'ABNAHMEUNTERSCHRIFT';
+    imagestring($canvas, 5, 20, 15, $title, $dark_blue);
+
+    // Metadaten Zeile 1
+    $line1 = 'Bericht: '.$bericht->ref.'   ·   '.trim($bericht->element_type.' '.$parent_ref);
+    imagestring($canvas, 4, 20, 50, $line1, $black);
+    // Zeile 2: Kunde
+    $line2 = 'Kunde: '.$kundename;
+    imagestring($canvas, 4, 20, 75, $line2, $black);
+    // Zeile 3: Datum + Zeit (Server) + Unterzeichner
+    $datetime = date('Y-m-d H:i:s');
+    $line3 = 'Zeit (Server): '.$datetime.'   ·   Unterzeichner: '.($signer_name ?: '—');
+    imagestring($canvas, 4, 20, 100, $line3, $black);
+    // Zeile 4: GPS
+    if ($gps_lat !== null && $gps_lon !== null) {
+        $line4 = sprintf('GPS: %.6f, %.6f', $gps_lat, $gps_lon);
+        imagestring($canvas, 3, 20, 125, $line4, $black);
+    }
+    // Bestätigungstext
+    $bestaetigung = 'Ich bestaetige hiermit die ordnungsgemaesse Ausfuehrung der dokumentierten Arbeiten.';
+    imagestring($canvas, 3, 20, 150, $bestaetigung, $black);
+
+    // Unterschrift-Bereich mittig einsetzen, auf Breite skalieren
+    $max_sig_w = $canvas_w - 80;
+    $max_sig_h = $sig_area_h - 60;
+    $ratio = min($max_sig_w / $sig_w, $max_sig_h / $sig_h);
+    $dw = (int) ($sig_w * $ratio);
+    $dh = (int) ($sig_h * $ratio);
+    $dx = (int) (($canvas_w - $dw) / 2);
+    $dy = $header_h + 30;
+    imagecopyresampled($canvas, $sig_img, $dx, $dy, 0, 0, $dw, $dh, $sig_w, $sig_h);
+    imagedestroy($sig_img);
+
+    // Trennlinie unter der Unterschrift
+    imageline($canvas, 40, $header_h + $sig_area_h - 20, $canvas_w - 40, $header_h + $sig_area_h - 20, $grey);
+    imagestring($canvas, 3, (int) ($canvas_w / 2 - 50), $header_h + $sig_area_h - 15,
+        'Unterschrift Kunde', $grey);
+
+    // Footer-Box mit Hash
+    $fy = $header_h + $sig_area_h;
+    imagefilledrectangle($canvas, 0, $fy, $canvas_w, $canvas_h, imagecolorallocate($canvas, 248, 248, 248));
+    imagerectangle($canvas, 0, $fy, $canvas_w - 1, $canvas_h - 1, $line_grey);
+    imagestring($canvas, 3, 20, $fy + 15, 'Integritaetspruefung (SHA-256 ueber alle vorherigen Seiten):', $grey);
+    imagestring($canvas, 2, 20, $fy + 40, $chain_hash, $black);
+    imagestring($canvas, 2, 20, $fy + 70, 'Erfasst: '.$datetime.' · Server: '.($_SERVER['SERVER_NAME'] ?? ''), $grey);
+
+    // Schreiben
     $filename = 'signature_'.dol_print_date(dol_now(), '%Y%m%d_%H%M%S').'.png';
     $target = $workdir.'/'.$filename;
-    if (!move_uploaded_file($_FILES['file']['tmp_name'], $target)) api_fail('Upload fehlgeschlagen', 500);
+    if (!imagepng($canvas, $target, 6)) api_fail('PNG schreiben fehlgeschlagen', 500);
+    imagedestroy($canvas);
     $relpath = str_replace(DOL_DATA_ROOT.'/', '', $target);
 
+    // Metadaten als JSON neben der Datei speichern (für spätere Verifikation)
+    $meta = array(
+        'bericht_id' => $bericht_id,
+        'bericht_ref' => $bericht->ref,
+        'parent_type' => $bericht->element_type,
+        'parent_ref' => $parent_ref,
+        'kunde' => $kundename,
+        'signer_name' => $signer_name,
+        'signed_at' => $datetime,
+        'signed_at_unix' => time(),
+        'user_id' => $user->id,
+        'user_login' => $user->login,
+        'gps_lat' => $gps_lat,
+        'gps_lon' => $gps_lon,
+        'chain_hash_sha256' => $chain_hash,
+        'page_count_at_signing' => count($prev_pages),
+        'remote_ip' => $_SERVER['REMOTE_ADDR'] ?? '',
+    );
+    @file_put_contents($target.'.meta.json', json_encode($meta, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE));
+
     $resm = $db->query("SELECT COALESCE(MAX(page_order),0) AS m FROM ".$db->prefix()."bericht_page WHERE fk_bericht = ".$bericht_id);
     $next = ($resm && ($o = $db->fetch_object($resm))) ? ((int) $o->m) + 1 : 1;
 
@@ -43,10 +162,15 @@ if ($method === 'POST' && $action === 'signature') {
     $page->page_order  = $next;
     $page->source_type = 'upload';
     $page->source_path = $relpath;
-    $page->note        = 'Unterschrift Kunde';
+    $page->note        = 'Unterschrift '.($signer_name ?: 'Kunde').' — '.$datetime;
     if ($page->create() <= 0) api_fail('Page-Insert fehlgeschlagen', 500);
 
-    api_ok(array('page_id' => $page->id, 'filename' => $filename));
+    api_ok(array(
+        'page_id' => $page->id,
+        'filename' => $filename,
+        'chain_hash' => $chain_hash,
+        'signed_at' => $datetime,
+    ));
 }
 
 $page_id = (int) ($_GET['id'] ?? 0);