feat(B-NOTIF): Notification→Message Konsolidierung — System-Channel, post_system_message(), Migration

B-NOTIF-SYS: CommConversation um is_system Feld erweitert, get_or_create_system_channel()
B-NOTIF-EVT: post_system_message() in kommunikation/services.py — erstellt CommMessage im System-Channel
- create_notification() als deprecated Wrapper delegiert auf post_system_message()
- Text-Block + action_card Block mit Deep-Link, Metadata: notification_type/severity/entity_ref
B-NOTIF-PREF: NotificationPreference als Routing-Konfiguration, stumm/disabled respektiert
B-NOTIF-MIG: Migration 0120 — Notifications → CommMessages migriert, notifications_legacy View
B-NOTIF-DEPREC: Notification-Routes als deprecated markiert, keine Routes entfernt
B-NOTIF-TEST: 19 Tests in test_notification_migration.py — alle grün
- System-Channel, post_system_message, create_notification Wrapper, Preferences, Unread-Badge, Migration Mapping, Sensitive Fields

app/core/notifications.py

@@ -1,7 +1,13 @@
-"""Notification service — create and manage user notifications."""
+"""Notification service — create and manage user notifications.
+
+As of B-NOTIF-EVT, the primary entry point is post_system_message() which posts
+to the Communication system channel. create_notification() is retained as a
+deprecated backward-compat wrapper that delegates to post_system_message().
+"""
 
 from __future__ import annotations
 
+import logging
 import uuid
 from datetime import UTC
 from typing import Any
@@ -15,6 +21,31 @@ from app.models.notification import (
     NotificationType,
 )
 
+logger = logging.getLogger(__name__)
+
+# Re-export post_system_message from kommunikation services for convenience
+async def post_system_message(
+    db: AsyncSession,
+    tenant_id: uuid.UUID,
+    user_id: uuid.UUID,
+    message_type: str,
+    title: str,
+    body: str | None = None,
+    entity_type: str | None = None,
+    entity_id: uuid.UUID | None = None,
+    severity: str = "info",
+):
+    """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.
+    """
+    from app.plugins.builtins.kommunikation.services import post_system_message as _post
+    return await _post(
+        db, tenant_id, user_id, message_type, title, body,
+        entity_type, entity_id, severity,
+    )
+
 
 async def create_notification(
     db: AsyncSession,
@@ -28,34 +59,24 @@ async def create_notification(
 ) -> Notification | None:
     """Create a new notification for a user if they have not disabled this type.
 
+    .. deprecated:: B-NOTIF-EVT
+        Use post_system_message() instead. This wrapper delegates to
+        post_system_message() and also creates a legacy Notification record
+        for backward compatibility with existing routes and frontend.
+
     Returns None if the user has opted out of this notification type.
     """
-    # Check user preference
-    pref = await db.execute(
-        select(NotificationPreference).where(
-            and_(
-                NotificationPreference.user_id == user_id,
-                NotificationPreference.type_key == type,
-                NotificationPreference.tenant_id == tenant_id,
-            )
-        )
+    # Delegate to post_system_message for the comm channel
+    comm_msg = await post_system_message(
+        db, tenant_id, user_id, type, title, body,
+        entity_type, entity_id, severity="info",
     )
-    pref_row = pref.scalar_one_or_none()
 
-    # If preference exists and is disabled, skip
-    if pref_row and not pref_row.is_enabled:
+    if comm_msg is None:
+        # User has muted this type — don't create legacy record either
         return None
 
-    # If no preference, check if type is enabled by default
-    if not pref_row:
-        type_def = await db.execute(
-            select(NotificationType).where(NotificationType.type_key == type)
-        )
-        type_row = type_def.scalar_one_or_none()
-        if type_row and not type_row.is_enabled_by_default:
-            return None
-
-    # Create notification
+    # Also create legacy Notification record for backward compat
     notif = Notification(
         tenant_id=tenant_id,
         user_id=user_id,
@@ -68,17 +89,18 @@ async def create_notification(
     db.add(notif)
     await db.flush()
 
-    # Publish notification.created event
+    # Publish notification.created event (backward compat)
     from app.core.event_bus import get_event_bus
     event_bus = get_event_bus()
-    await event_bus.publish('notification.created', {
-        'notification_id': str(notif.id),
-        'tenant_id': str(tenant_id),
-        'user_id': str(user_id),
-        'type': type,
-        'title': title,
-        'entity_type': entity_type,
-        'entity_id': str(entity_id) if entity_id else None,
+    await event_bus.publish("notification.created", {
+        "notification_id": str(notif.id),
+        "tenant_id": str(tenant_id),
+        "user_id": str(user_id),
+        "type": type,
+        "title": title,
+        "entity_type": entity_type,
+        "entity_id": str(entity_id) if entity_id else None,
+        "comm_message_id": str(comm_msg.id),
     })
 
     return notif
@@ -93,7 +115,6 @@ async def list_notifications(
 ) -> dict[str, Any]:
     """List notifications for a user, unread first, then by created_at desc."""
     offset = (page - 1) * page_size
-    # Count total
     count_q = (
         select(func.count())
         .select_from(Notification)
@@ -104,7 +125,6 @@ async def list_notifications(
     )
     total = (await db.execute(count_q)).scalar() or 0
 
-    # Query — unread first (read_at IS NULL), then newest
     q = (
         select(Notification)
         .where(
@@ -112,7 +132,7 @@ async def list_notifications(
             Notification.user_id == user_id,
         )
         .order_by(
-            Notification.read_at.isnot(None),  # False (unread) sorts first
+            Notification.read_at.isnot(None),
             Notification.created_at.desc(),
         )
         .offset(offset)