fix: prevent NameError when QU disabled and fix connection leak

- Add route="vector" and sql_query=None defaults before the
`if qu_enabled:` block in both app_cli.py and app_web.py,
preventing NameError when query understanding is disabled.
- Wrap sqlite3 connection in try/finally in sql_retriever.py
to ensure conn.close() runs even if execute/fetchmany raises.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app_cli.py

@@ -275,6 +275,8 @@ def main() -> None:
         original_query = user_input
         search_query = user_input
         display_query = user_input
+        route = "vector"
+        sql_query = None
 
         if qu_enabled:
             with console.status("[bold blue]Understanding your question...[/bold blue]"):

app_web.py

@@ -154,6 +154,8 @@ def render_chat():
 
         search_query = combined
         display_query = combined
+        route = "vector"
+        sql_query = None
         max_clarifications = qu_cfg.get("max_clarifications", 1)
 
         if qu_enabled:

src/sql_retriever.py

@@ -51,12 +51,13 @@ def execute_sql_query(sql_query: str, cfg: dict) -> list[dict]:
 
     try:
         conn = sqlite3.connect(f"file:{db_path}?mode=ro", uri=True)
-        conn.row_factory = sqlite3.Row
-        cursor = conn.execute(sql_query)
-        rows = cursor.fetchmany(max_rows)
-        result = [dict(row) for row in rows]
-        conn.close()
-        return result
+        try:
+            conn.row_factory = sqlite3.Row
+            cursor = conn.execute(sql_query)
+            rows = cursor.fetchmany(max_rows)
+            return [dict(row) for row in rows]
+        finally:
+            conn.close()
     except Exception:
         return []