Clean usage of conversation_id in chat API function

- Normalize conversation_id type to str instead of str or UUID
- Do not pass conversation_id to agenerate_chat_response as
  the associated conversation is also being passed. So can get its id
  directly.

src/khoj/routers/api_chat.py

@@ -860,9 +860,9 @@ async def chat(
             async for result in send_llm_response(f"Conversation {conversation_id} not found", tracer.get("usage")):
                 yield result
             return
-        conversation_id = conversation.id
+        conversation_id = str(conversation.id)
 
-        async for event in send_event(ChatEvent.METADATA, {"conversationId": str(conversation_id), "turnId": turn_id}):
+        async for event in send_event(ChatEvent.METADATA, {"conversationId": conversation_id, "turnId": turn_id}):
             yield event
 
         agent: Agent | None = None
@@ -1383,7 +1383,6 @@ async def chat(
             conversation_commands,
             user,
             request.user.client_app,
-            conversation_id,
             location,
             user_name,
             researched_results,

src/khoj/routers/helpers.py

@@ -1359,7 +1359,6 @@ async def agenerate_chat_response(
     conversation_commands: List[ConversationCommand] = [ConversationCommand.Default],
     user: KhojUser = None,
     client_application: ClientApplication = None,
-    conversation_id: str = None,
     location_data: LocationData = None,
     user_name: Optional[str] = None,
     meta_research: str = "",
@@ -1394,7 +1393,7 @@ async def agenerate_chat_response(
             operator_results=operator_results,
             inferred_queries=inferred_queries,
             client_application=client_application,
-            conversation_id=conversation_id,
+            conversation_id=str(conversation.id),
             query_images=query_images,
             train_of_thought=train_of_thought,
             raw_query_files=raw_query_files,