feat: Add library directive to multiple BLoC and service files for improved organization

lib/components/account/balances_tab.dart

@@ -3,6 +3,7 @@
 /// the amount they owe, and their overall balance status (to pay, to receive, or balanced).
 ///
 /// The widget handles both light and dark themes and provides a fallback UI for empty balance lists.
+library;
 
 import 'package:flutter/material.dart';
 import '../../models/user_balance.dart';