Fix: Add fallback database path when /data not available in HF Spaces

If HF Persistent Storage is not enabled, /data won't be accessible.
This fix adds a fallback to /tmp/agentgraph for ephemeral storage.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

utils/config.py

@@ -53,15 +53,28 @@ if LANGFUSE_PUBLIC_KEY and LANGFUSE_SECRET_KEY:
 ANTHROPIC_API_KEY = os.getenv("ANTHROPIC_API_KEY")
 
 # Database Configuration
-# For HF Spaces, use /data persistent storage directory
+# For HF Spaces, use /data persistent storage directory if available
+# Fall back to /tmp if /data is not accessible (Persistent Storage not enabled)
 # For local development, use datasets/db directory
 def _get_default_db_uri():
     """Get default database URI based on environment."""
     if os.getenv("SPACE_ID"):  # HF Spaces
-        # Use HF Persistent Storage at /data
-        # Note: /data directory is created by HF when Persistent Storage is enabled
-        # The directory creation is attempted at database init time, not config load time
-        return "sqlite:////data/agent_monitoring.db"
+        # Try to use HF Persistent Storage at /data first
+        data_dir = Path("/data")
+        try:
+            # Check if /data exists and is writable
+            data_dir.mkdir(parents=True, exist_ok=True)
+            test_file = data_dir / ".write_test"
+            test_file.touch()
+            test_file.unlink()
+            print("✅ Using HF Persistent Storage at /data")
+            return "sqlite:////data/agent_monitoring.db"
+        except (OSError, PermissionError) as e:
+            # Fall back to /tmp if /data is not available
+            print(f"⚠️ /data not available ({e}), using /tmp for ephemeral storage")
+            tmp_dir = Path("/tmp/agentgraph")
+            tmp_dir.mkdir(parents=True, exist_ok=True)
+            return f"sqlite:///{tmp_dir}/agent_monitoring.db"
     else:
         # Local development - use datasets/db relative to project root
         project_root = Path(__file__).parent.parent.resolve()