Update app.py

app.py

@@ -252,7 +252,7 @@ def _load_block_catalog(block_type: str) -> Dict:
     Loads the Scratch block catalog named '{block_type}_blocks.json'
     from the <project_root>/blocks/ folder. Returns {} on any error.
     """
-    catalog_path = BLOCKS_DIR / f"{block_type}_blocks.json"
+    catalog_path = BLOCKS_DIR / f"{block_type}.json"
 
     try:
         text = catalog_path.read_text()  # will raise FileNotFoundError if missing