fix: Improve delete operations with existence checks

- Update delete functions to return bool indicating success
- Add existence checks before deleting items
- Return 404 error for non-existent items in RPC delete operations
- Remove unused 'new_response_ok' result from RPC delete operations

lib/schemas/jsonrpc/model_response.v

@@ -51,7 +51,7 @@ pub fn new_response_true(id int) Response {
 pub fn new_response_ok(id int) Response {
 	return Response{
 		jsonrpc: jsonrpc_version
-		result:  ''
+		result:  'true'
 		id:      id
 	}
 }
@@ -96,9 +96,6 @@ pub fn new_error_response(id int, error RPCError) Response {
 	}
 }
 
-
-
-
 // decode_response parses a JSON string into a Response object.
 // This function handles the complex validation rules for JSON-RPC responses.
 //