impr: update when database changed, instead of showEvent

ui/extends/shared/database.py

@@ -1,6 +1,6 @@
 from typing import Type
 
-from PySide6.QtCore import QUrl
+from PySide6.QtCore import QObject, QUrl, Signal
 from sqlalchemy import Engine
 from sqlalchemy import create_engine as sa_create_engine
 from sqlalchemy.pool import NullPool, Pool
@@ -9,3 +9,10 @@ from sqlalchemy.pool import NullPool, Pool
 def create_engine(_url: str | QUrl, pool: Type[Pool] = NullPool) -> Engine:
     url = _url.toString() if isinstance(_url, QUrl) else _url
     return sa_create_engine(url, poolclass=pool)
+
+
+class DatabaseUpdateSignals(QObject):
+    songDataUpdated = Signal()
+
+
+databaseUpdateSignals = DatabaseUpdateSignals()