Restructure: Move 43 files into 8 domain packages (backend-lehrer)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend-lehrer/messenger_api.py

@@ -1,21 +1,4 @@
-"""
-BreakPilot Messenger API — Barrel Re-export.
-
-Stellt Endpoints fuer Kontakte, Konversationen, Nachrichten,
-CSV-Import, Gruppenmanagement und Templates bereit.
-
-Split into:
-  - messenger_models.py: Pydantic models
-  - messenger_helpers.py: JSON file storage & default templates
-  - messenger_contacts.py: Contact CRUD & CSV import/export
-  - messenger_conversations.py: Conversations, messages, groups, templates, stats
-"""
-
-from fastapi import APIRouter
-
-from messenger_contacts import router as _contacts_router
-from messenger_conversations import router as _conversations_router
-
-router = APIRouter(prefix="/api/messenger", tags=["Messenger"])
-router.include_router(_contacts_router)
-router.include_router(_conversations_router)
+# Backward-compat shim -- module moved to messenger/api.py
+import importlib as _importlib
+import sys as _sys
+_sys.modules[__name__] = _importlib.import_module("messenger.api")