Update app.py to include ROOT path

Add ROOT path to sys.path for module resolution

scheduler/dashboard/app.py

@@ -5,6 +5,12 @@ Launch with: uv run court-scheduler dashboard
 """
 
 from __future__ import annotations
+import sys
+from pathlib import Path
+
+ROOT = Path("/app")  # absolute, unambiguous
+if str(ROOT) not in sys.path:
+    sys.path.insert(0, str(ROOT))
 
 import subprocess
 from pathlib import Path