fix: ensure data directory exists before DB connection in all threads

.gitignore

@@ -2,3 +2,4 @@
 __pycache__/
 *.pyc
 config.yaml
+data/

src/database.py

@@ -49,6 +49,7 @@ def init_db():
 
 def _get_conn() -> sqlite3.Connection:
     if not hasattr(_local, "conn") or _local.conn is None:
+        DB_PATH.parent.mkdir(parents=True, exist_ok=True)
         _local.conn = sqlite3.connect(str(DB_PATH), timeout=10)
         _local.conn.execute("PRAGMA journal_mode=WAL")
         _local.conn.execute("PRAGMA busy_timeout=5000")