Handle DuckDB lock errors gracefully in UI

- Catch IOException when engine holds exclusive lock
- Show informative message instead of crashing

src/tradefinder/ui/app.py

@@ -9,6 +9,7 @@ from __future__ import annotations
 from datetime import datetime
 from typing import Any
 
+import duckdb
 import streamlit as st
 import structlog
 
@@ -34,8 +35,11 @@ def get_storage() -> DataStorage | None:
         return None
 
     storage = DataStorage(db_path, read_only=True)
-    storage.connect()
+    try:
-    return storage
+        storage.connect()
+        return storage
+    except duckdb.IOException:
+        return None
 
 
 @st.cache_data(ttl=30)
@@ -103,9 +107,16 @@ def render_database_status() -> None:
     """Render database connection status."""
     st.subheader("Database Status")
 
+    settings = get_settings()
+    db_path = settings.duckdb_path
+
+    if not db_path.exists():
+        st.warning("Database not initialized yet. Start the trading engine first.")
+        return
+
     storage = get_storage()
     if storage is None:
-        st.warning("Database not initialized yet. Start the trading engine first.")
+        st.info(f"Database exists at {db_path} (engine has exclusive lock)")
         return
 
     try: