refactor(routes): move webhook domain into routes/webhook/ subpackage

app.py

@@ -820,7 +820,7 @@ async def _stop_background():
 logger.info("AI interaction tools initialized (session, memory, RAG, UI control)")
 
 # Webhooks
-from routes.webhook_routes import setup_webhook_routes
+from routes.webhook.webhook_routes import setup_webhook_routes
 app.include_router(setup_webhook_routes(webhook_manager, auth_manager, session_manager, api_key_manager))
 
 # API Tokens

routes/webhook/__init__.py

@@ -0,0 +1,5 @@
+"""Webhook route domain package (slice 2l, #4082/#4071).
+
+Contains webhook_routes.py, migrated from the flat routes/ directory.
+Backward-compat shim at routes/webhook_routes.py re-exports from here.
+"""