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

app/plugins/builtins/report_generator/plugin.py

@@ -3,7 +3,13 @@
 from __future__ import annotations
 
 from app.plugins.base import BasePlugin
-from app.plugins.manifest import FrontendMenuItem, FrontendPageRoute, PluginManifest, PluginRouteDef
+from app.plugins.manifest import (
+    FrontendMenuItem,
+    FrontendPageRoute,
+    FrontendSettingsPage,
+    PluginManifest,
+    PluginRouteDef,
+)
 
 
 class ReportGeneratorPlugin(BasePlugin):
@@ -17,12 +23,31 @@ class ReportGeneratorPlugin(BasePlugin):
         is_core=True,
         dependencies=["permissions"],
         routes=[
+            # documents router MUST be registered before routes: its fixed
+            # single-segment paths (/letterheads, /print-templates, ...) would
+            # otherwise be shadowed by the /{report_id} catch-all in routes.
+            PluginRouteDef(
+                path="/api/v1/reports",
+                module="app.plugins.builtins.report_generator.documents",
+                router_attr="router",
+            ),
             PluginRouteDef(
                 path="/api/v1/reports",
                 module="app.plugins.builtins.report_generator.routes",
                 router_attr="router",
             ),
         ],
+        settings_pages=[
+            FrontendSettingsPage(
+                path="documents",
+                label_key="settings.documents",
+                label="Dokumente",
+                component="@/pages/DocumentSettings",
+                icon="FileText",
+                order=75,
+                permission="reports:read",
+            ),
+        ],
         events=["report.requested", "report.generated"],
         migrations=["0001_initial.sql", "0002_reports_folder_id.sql"],
         permissions=["reports:read", "reports:generate", "reports:manage_templates"],
@@ -38,8 +63,20 @@ class ReportGeneratorPlugin(BasePlugin):
         contract_version="1.0.0")
 
     def get_entity_models(self) -> dict[str, type]:
-        from app.plugins.builtins.report_generator.models import ReportInstance, ReportTemplate
-        return {"report_template": ReportTemplate, "report_instance": ReportInstance}
+        from app.plugins.builtins.report_generator.models import (
+            DocumentAsset,
+            Letterhead,
+            PrintTemplate,
+            ReportInstance,
+            ReportTemplate,
+        )
+        return {
+            "report_template": ReportTemplate,
+            "report_instance": ReportInstance,
+            "letterhead": Letterhead,
+            "print_template": PrintTemplate,
+            "document_asset": DocumentAsset,
+        }
 
     async def on_activate(
         self, db, service_container, event_bus