feat(L1-L3): Dokumente-Generator — Briefpapier+Block-System+Drag&Drop-Editor+Renderer

- Briefpapier (letterheads): Seiten-Setup (A4/A5/Letter, Ränder), Header/Footer-Blöcke, Wasserzeichen, Logo-Upload (DocumentAsset, data:-URI-only)
- Druckvorlagen (print_templates): Block-Komposition mit Briefpapier-Ref + entity_type
- Block-Registry (document_blocks.py): text/image/shape(line/rect/circle)/table/spacer/divider/placeholder/pagebreak + Modul-Beiträge via document_blocks()-Contract
- Renderer (document_renderer.py): Blocks→HTML→PDF via WeasyPrint (SSRF-Sandbox data:-URI-only), @page-Frame mit running header/footer, Placeholder-Beispiel-Defaults gegen StrictUndefined
- Contract-Beitrag contacts: document_placeholders/document_data (#359-Muster wie importexport_entities)
- 13 neue Endpoints in documents.py: Letterhead-CRUD, Template-CRUD, Assets, document-blocks, document-placeholders, preview (HTML), render (PDF)
- Migration: Plugin-SQL 0003 (idempotent) + Alembic 0143 (Dual-Path, RLS fail-closed crm_api)
- Frontend: api/documents.ts, Settings→Dokumente (settings_pages), BlockEditor (@dnd-kit Palette/Canvas/Config/Live-Preview-iframe), LetterheadEditor, PrintTemplateEditor, DocumentGenerationDialog (global, ContactDetailPage-Integration)
- i18n de/en, api-documentation.md, plugin-development-guide.md, PROGRESS.md

Verifikation: 32/32 neue Tests + 9/9 Regressionen, tsc exit 0, Build OK 2.79s, Alembic-Fresh-DB 0143 mit RLS bewiesen, ruff clean

frontend/src/pages/ContactDetailPage.tsx

@@ -2,7 +2,7 @@
  * Contact Detail Page — loads a single contact by ID from route params.
  */
 
-import React from 'react';
+import React, { useState } from 'react';
 import { useParams, useNavigate } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
 import { ContactDetail } from '@/components/contacts/ContactDetail';
@@ -10,8 +10,9 @@ import { ContactEditForm } from '@/components/contacts/ContactEditForm';
 import { useWindowStore } from '@/store/windowStore';
 import { useUnifiedContact, type UnifiedContact } from '@/api/hooks';
 import { Button } from '@/components/ui/Button';
-import { ChevronLeft } from 'lucide-react';
+import { ChevronLeft, FileText } from 'lucide-react';
 import { PrintButton } from '@/components/common/PrintButton';
+import { DocumentGenerationDialog } from '@/components/documents/DocumentGenerationDialog';
 import { usePermission } from '@/hooks/usePermission';
 import { useAuthStore } from '@/store/authStore';
 
@@ -23,6 +24,7 @@ export function ContactDetailPage() {
   const openWindow = useWindowStore((s) => s.openWindow);
   const { hasPermission } = usePermission();
   const authUser = useAuthStore((state) => state.user);
+  const [docDialogOpen, setDocDialogOpen] = useState(false);
   const canAccess = (perm: string): boolean => {
     return hasPermission(perm);
   };
@@ -59,6 +61,17 @@ export function ContactDetailPage() {
         </button>
         <div className="flex-1" />
         {canAccess('contacts:read') && <PrintButton targetId="contact-detail" />}
+        {canAccess('reports:generate') && (
+          <button
+            onClick={() => setDocDialogOpen(true)}
+            className="inline-flex items-center gap-1 px-2 py-1 rounded text-sm text-secondary-700 hover:bg-secondary-100 min-h-touch"
+            aria-label={t('documents.dialog.title', 'Dokument erstellen')}
+            title={t('documents.dialog.title', 'Dokument erstellen')}
+            data-testid="contact-detail-document-button"
+          >
+            <FileText className="w-4 h-4" aria-hidden="true" strokeWidth={2} />
+          </button>
+        )}
       </div>
       <div className="flex-1 overflow-y-auto" id="contact-detail">
         <ContactDetail
@@ -68,6 +81,15 @@ export function ContactDetailPage() {
           onDeleted={handleDeleted}
         />
       </div>
+      {contact && (
+        <DocumentGenerationDialog
+          open={docDialogOpen}
+          onClose={() => setDocDialogOpen(false)}
+          entityType={contact.type === 'company' ? 'company' : 'contact'}
+          entityId={contact.id}
+          entityLabel={contact.displayname}
+        />
+      )}
     </div>
   );
 }