refactor: frontend preparation script with error handling

- Added a check to ensure the script is run from the project root by verifying the existence of pyproject.toml.
- Implemented a safeguard against removing the TARGET directory if it is a symlink, raising an appropriate error message.

scripts/prepare_frontend_dir.py

@@ -1,10 +1,14 @@
-#!/usr/bin/env python3
 from pathlib import Path
 import shutil
 
 TARGET = Path("meshchatx") / "public"
 
+if not Path("pyproject.toml").exists():
+    raise RuntimeError("Must run from project root")
+
 if TARGET.exists():
+    if TARGET.is_symlink():
+        raise RuntimeError(f"{TARGET} is a symlink, refusing to remove")
     shutil.rmtree(TARGET)
 
 TARGET.mkdir(parents=True, exist_ok=True)