impr(db): close connection when program exit using atexit hook

src/arcaea_offline/database.py

@@ -1,3 +1,4 @@
+import atexit
 import os
 import sqlite3
 from dataclasses import fields, is_dataclass
@@ -30,6 +31,8 @@ class Database(metaclass=Singleton):
         self.__conn.execute("PRAGMA journal_mode = WAL;")
         self.__conn.execute("PRAGMA foreign_keys = ON;")
 
+        atexit.register(self.__conn.close)
+
         self.__update_hooks = []
 
     @property