feat(UI-Overhaul-Phase2): AI Assistent in Kommunikation integriert

Migration 0137: Drop AI chat tables (ai_chat_sessions, ai_chat_messages, ai_chat_attachments, ai_conversations, ai_messages)

Backend:
- Remove AIChatSession, AIChatMessage, AIChatAttachment models from ai_assistant/models.py
- Remove AIConversation, AIMessage from app/models/__init__.py
- Remove session/message/stream/attachment routes from ai_assistant/routes.py
- Add new streaming route POST /ai/conversations/{conversation_id}/stream using comm tables
- Add new messages route GET /ai/conversations/{conversation_id}/messages using comm tables
- Add stream_chat_comm, get_comm_messages, save_comm_message to services.py
- Update external_api.py to use CommConversation/CommMessage instead of AIChatSession/AIChatMessage
- Update unified_search ai_chat_provider to search comm_messages with conversation_type=ai
- Remove ai_copilot router from main.py and routes/__init__.py
- Remove ai_conversation from entity_permissions.py and owner_transfer_service.py
- Update ai_assistant/plugin.py get_entity_models to remove AIChatSession
- Guard ai_copilot_service.py imports with try/except

Frontend:
- Remove AIAssistant.tsx, AIAssistantStandalone.tsx, SessionList.tsx, ChatWindow.tsx
- Remove AI Assistant routes from routes/index.tsx
- Update api/ai.ts: streamChat uses /ai/conversations/{id}/stream, fetchMessages uses /ai/conversations/{id}/messages
- Update Communication.tsx: use convId for AI streaming, remove aiSessionId, use fetchAiMessages for AI conversations
- Update AiChatPanel.tsx: create comm conversation instead of AI session, use new fetchMessages
- Update AISidebar.tsx: remove ChatWindow import, show placeholder

tsc clean, build successful, backend import OK

app/plugins/builtins/ai_assistant/external_api.py

@@ -80,26 +80,29 @@ async def run_agent_external(
 
     # Create or find a session for this external interaction
 
-    from app.plugins.builtins.ai_assistant.models import AIChatMessage, AIChatSession
+    # AIChatSession/AIChatMessage removed — using comm tables
 
-    session = AIChatSession(
-        user_id=uuid.UUID(current_user["user_id"]),
-        agent_id=agent.id,
-        title=f"External: {data.message[:50]}" if data.message else "External Agent Run",
-        is_sidebar=False,
+    # Create a comm conversation for this external interaction
+    from app.plugins.builtins.kommunikation.models import CommConversation
+    session = CommConversation(
         tenant_id=tenant_id,
+        title=f"External: {data.message[:50]}" if data.message else "External Agent Run",
         owner_id=uuid.UUID(current_user["user_id"]),
+        created_by=uuid.UUID(current_user["user_id"]),
+        created_by_type="user",
+        metadata_={"conversation_type": "ai", "agent_id": str(agent.id)},
     )
     db.add(session)
     await db.flush()
 
     # Store the user message
-    user_msg = AIChatMessage(
-        session_id=session.id,
-        role="user",
+    from app.plugins.builtins.kommunikation.models import CommMessage
+    user_msg = CommMessage(
+        conversation_id=session.id,
+        sender_id=uuid.UUID(current_user["user_id"]),
+        sender_type="user",
         content=data.message,
-        tokens=0,
-        model_used=agent.name or "external",
+        content_format="text",
         tenant_id=tenant_id,
     )
     db.add(user_msg)
@@ -117,7 +120,7 @@ async def run_agent_external(
     }
 
     # Run the agent via streaming chat (non-streaming mode)
-    from app.plugins.builtins.ai_assistant.services import stream_chat
+    from app.plugins.builtins.ai_assistant.services import stream_chat_comm
 
     full_response = ""
     async with get_db() as stream_db:
@@ -250,15 +253,16 @@ async def stream_agent_external(
         raise HTTPException(status_code=400, detail="Agent is not active")
 
     # Create session
-    from app.plugins.builtins.ai_assistant.models import AIChatSession
+    # AIChatSession removed — using comm tables
 
-    session = AIChatSession(
-        user_id=uuid.UUID(current_user["user_id"]),
-        agent_id=agent.id,
-        title=f"External Stream: {data.message[:50]}" if data.message else "External Agent Stream",
-        is_sidebar=False,
+    from app.plugins.builtins.kommunikation.models import CommConversation
+    session = CommConversation(
         tenant_id=tenant_id,
+        title=f"External Stream: {data.message[:50]}" if data.message else "External Agent Stream",
         owner_id=uuid.UUID(current_user["user_id"]),
+        created_by=uuid.UUID(current_user["user_id"]),
+        created_by_type="user",
+        metadata_={"conversation_type": "ai", "agent_id": str(agent.id)},
     )
     db.add(session)
     await db.commit()
@@ -274,15 +278,15 @@ async def stream_agent_external(
         "field_permissions": current_user.get("field_permissions", {}),
     }
 
-    from app.plugins.builtins.ai_assistant.services import stream_chat
+    from app.plugins.builtins.ai_assistant.services import stream_chat_comm
 
     async def event_stream():
         from app.core.db import get_session_factory
         factory = get_session_factory()
         async with factory() as stream_db:
             await set_tenant_context(stream_db, tenant_id)
-            async for chunk in stream_chat(
-                stream_db, session, agent, data.message, user_context, tenant_id
+            async for chunk in stream_chat_comm(
+                stream_db, session.id, agent, data.message, user_context, tenant_id, uuid.UUID(current_user["user_id"])
             ):
                 yield chunk
         yield "data: [DONE]\n\n"