Refactor backend to use request-scoped SQLite connections

backend/app/db.py

@@ -125,3 +125,18 @@ async def init_db(db: aiosqlite.Connection) -> None:
         await db.executescript(statement)
     await db.commit()
     log.info("database_schema_ready")
+
+
+async def open_db(database_path: str) -> aiosqlite.Connection:
+    """Open a new application SQLite connection with the standard settings.
+
+    Args:
+        database_path: Path to the BanGUI SQLite database.
+
+    Returns:
+        A configured :class:`aiosqlite.Connection` instance.
+    """
+    db = await aiosqlite.connect(database_path)
+    db.row_factory = aiosqlite.Row
+    await db.execute("PRAGMA foreign_keys=ON;")
+    return db