Refactor of query handlers

Author: asimurka

src/client.py

@@ -36,10 +36,17 @@ async def load(self, llama_stack_config: LlamaStackConfiguration) -> None:
         if self._lsc is not None:  # early stopping - client already initialized
             return
 
-        if llama_stack_config.use_as_library_client:
-            await self._load_library_client(llama_stack_config)
-        else:
-            self._load_service_client(llama_stack_config)
+        try:
+            if llama_stack_config.use_as_library_client:
+                await self._load_library_client(llama_stack_config)
+            else:
+                self._load_service_client(llama_stack_config)
+        except APIConnectionError as e:
+            error_response = ServiceUnavailableResponse(
+                backend_name="Llama Stack",
+                cause=str(e),
+            )
+            raise HTTPException(**error_response.model_dump()) from e
 
     async def _load_library_client(self, config: LlamaStackConfiguration) -> None:
         """Initialize client in library mode.