fix(arch): externes Audit — 13 Backend-Fixes (Workspace-Modules, Tenant-Manifeste, Lifecycle, Contracts, Permissions)

Verifikation: Alle 17 Audit-Findings gegen den Code geprueft — alle bestaetigt.
Backend-Lifecycle-Fixes umgesetzt; 4 Frontend-Plugin-Architektur-Punkte
als Phase Q in die Roadmap eingeplant.

- P1 list_workspaces: Module + User-Counts gebuendelt laden (Editor-Overwrite-Bug)
- P1 active-manifests: Tenant-Deaktivierung (tenant_plugin_activation) filtern
- P1 uninstall: volle Service-Deactivation VOR registry.uninstall()
- P1 ContractRegistry: DB-Aktivstatus-Guard (Restart-Edge-Case) + Re-Activate
- P1/P2 Field-Definitions: voller Lifecycle (register/unregister) im Service
- P1/P2 Contact-Felddefinitionen (39) ins ContactsPlugin-Manifest verschoben
- P1 12 fehlende Permission-Keys registriert (AST-Scan: 0 fehlend)
- P2 contact_folder -> ContactsPlugin; ENTITY_PLUGIN_OWNERS wird befuellt
- P2 Entity-Permission-Fallback fail-closed statt contacts:read
- P2 forgejo_error_reporter is_core=False; DMS is_core=True (ADR-020)
- P2 Worker: Contacts-Trash-Cleanup ins Plugin (get_job_modules-Discovery)
- P1/P2 DSGVO-Export delegiert an DSAR-Collector (kein Core->Contacts)
- P2 False-green Tests korrigiert (or True, veraltete Route-Count-Assertion)

Verifikation: tests/test_audit_architecture_fixes.py 17/17; Regressionen
gruen (contacts_lifecycle, entity_registry, workspace_scopes, rbac,
lifecycle_service); Combo-Order-Test 35/35; Cross-Plugin-Checker 497/0;
compileall sauber; ruff auf 7-Error-Baseline.

Doku: PROGRESS.md Audit-Section, PLATFORM_ROADMAP.md Phase Q (Q1-Q4),
plugin-development-guide.md Lifecycle, permissions.md Katalog.

app/plugins/builtins/dms/plugin.py

@@ -20,6 +20,11 @@ class DmsPlugin(BasePlugin):
         version="1.0.0",
         display_name="DMS",
         description="Document management: folder hierarchy, file upload, PDF preview, Collabora edit sessions, internal sharing, search, bulk ops.",
+        # Audit P1/P2 (ADR-020): DMS is a platform core plugin — the core schema
+        # (entity_attachments.files-FK) builds on the DMS files table, so DMS
+        # cannot be deactivated. Declared is_core=True so the registry enforces
+        # this instead of the FK being silently invalid.
+        is_core=True,
         dependencies=["permissions"],
         routes=[
             PluginRouteDef(