fix: handle permission errors when browsing directories

dashboard/backend/routers/files.py

@@ -66,8 +66,18 @@ def browse(path: str = ""):
         target = _safe_path(path)
     except ValueError:
         raise HTTPException(status_code=403, detail="Access denied")
+
+    # Check if we have permission to read the directory
+    try:
+        items = list(target.iterdir())
+    except PermissionError:
+        raise HTTPException(status_code=403, detail="Permission denied")
+    except OSError as e:
+        logger.error(f"Error reading directory {target}: {e}")
+        raise HTTPException(status_code=500, detail="Error reading directory")
+
     entries = []
-    for item in sorted(target.iterdir()):
+    for item in sorted(items):
         try:
             if not _is_safe_symlink(item):
                 continue