Fallback to writable data dir when /data is not mountable on HF Spaces.

multi_llm_chatbot_backend/app/core/db.py

@@ -89,9 +89,18 @@ _TABLE_NAMES = {t[0] for t in _TABLES}
 
 def _data_dir() -> Path:
     raw = os.environ.get("DATA_DIR") or "/data"
-    p = Path(raw).expanduser()
-    p.mkdir(parents=True, exist_ok=True)
-    return p
+    candidates = [Path(raw).expanduser()]
+    if str(candidates[0]) == "/data":
+        candidates.append(Path.home() / "data")
+    for p in candidates:
+        try:
+            p.mkdir(parents=True, exist_ok=True)
+            return p
+        except PermissionError:
+            LOG.warning("Cannot create data dir %s; trying fallback", p)
+    fallback = Path("/tmp/data")
+    fallback.mkdir(parents=True, exist_ok=True)
+    return fallback
 
 
 def _db_path() -> Path: