feat: moved LLMConfigs from User to SearchSpaces

- RBAC soon??
- Updated various services and routes to handle search space-specific LLM preferences.
- Modified frontend components to pass search space ID for LLM configuration management.
- Removed onboarding page and settings page as part of the refactor.

surfsense_backend/app/agents/researcher/qna_agent/nodes.py

@@ -101,11 +101,12 @@ async def answer_question(state: State, config: RunnableConfig) -> dict[str, Any
     documents = state.reranked_documents
     user_query = configuration.user_query
     user_id = configuration.user_id
+    search_space_id = configuration.search_space_id
 
     # Get user's fast LLM
-    llm = await get_user_fast_llm(state.db_session, user_id)
+    llm = await get_user_fast_llm(state.db_session, user_id, search_space_id)
     if not llm:
-        error_message = f"No fast LLM configured for user {user_id}"
+        error_message = f"No fast LLM configured for user {user_id} in search space {search_space_id}"
         print(error_message)
         raise RuntimeError(error_message)