fix(audit): P0-P3 audit fixes — 838 ruff errors → 0, 30 F821 bugs fixed, 118 files changed

- P0: hooks.py 3-tuple fix, trigger_dispatcher Contract, contacts/plugin unregister_actions_by_owner
- P0: 5 test files — check_permission mocks removed, hardcoded DB credential → env var
- P1: attachment_service DmsFile via Contract helper, restore_registry/history_hooks dedup
- P1: mail/plugin restore unregister, mcp_client datetime.now(UTC), saved_views/filters patterns
- P1: ProtectedRoute fail-closed, 13 test assertion fixes (bcrypt, DB-URLs, SECRET_KEYs)
- P2: deprecated notifications → post_system_message (3 files), forgejo Base, report_generator lazy import
- P2: webhooks permissions, deps.py/roles.py plugin perms removed, import_export default
- P2: address/tags/entity_links patterns removed, worker.py Contract-Umgehungen fixed
- P2: 28 frontend TODOs (hardcoded constants, deprecated notification API)
- P3: dead code, duplicates, deprecated imports, private attr, __import__ inline
- P3: 8 frontend TODOs (LucideIcons, inline styles, XSS, i18n)
- ruff: 838 → 0 (612 auto-fix + 246 manual + 27 F821 regression fix)
- F821: 30 → 0 (AutomationDefinition, DmsFile, user_id, Path, Any, String)
- Contract-Umgehungen: 2 neue gefunden (worker.py:169, worker.py:280) und gefixt

app/core/notifications.py

@@ -12,13 +12,11 @@ import uuid
 from datetime import UTC
 from typing import Any
 
-from sqlalchemy import and_, func, select, update
+from sqlalchemy import func, select, update
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.models.notification import (
     Notification,
-    NotificationPreference,
-    NotificationType,
 )
 
 logger = logging.getLogger(__name__)
@@ -37,11 +35,15 @@ async def post_system_message(
 ):
     """Post a typed system message to the tenant system channel.
 
-    Delegates to kommunikation.services.post_system_message.
-    Returns the created CommMessage, or None if the user has muted this type.
+    Delegates to kommunikation plugin via contract registry. Returns None
+    if the kommunikation plugin is not active (graceful degradation).
     """
-    from app.plugins.builtins.kommunikation.services import post_system_message as _post
-    return await _post(
+    from app.plugins.builtins.contracts import get_contract
+    komm_contract = get_contract("kommunikation")
+    if komm_contract is None:
+        logger.warning("kommunikation plugin not available — system message not posted")
+        return None
+    return await komm_contract.post_system_message(
         db, tenant_id, user_id, message_type, title, body,
         entity_type, entity_id, severity,
     )