feat: Implement account management features

- Added ExpenseDetailDialog for displaying expense details and actions.
- Created ExpensesTab to list expenses for a group.
- Developed GroupExpensesPage to manage group expenses with tabs for expenses, balances, and settlements.
- Introduced SettlementsTab to show optimized repayment plans.
- Refactored create_trip_content.dart to remove CountBloc and related logic.
- Added Account model to manage user accounts and group members.
- Replaced CountRepository with AccountRepository for account-related operations.
- Removed CountService and CountRepository as part of the refactor.
- Updated main.dart and home.dart to integrate new account management components.

lib/components/account/balances_tab.dart

@@ -0,0 +1,124 @@
+import 'package:flutter/material.dart';
+import '../../data/models/balance.dart';
+
+class BalancesTab extends StatelessWidget {
+  final List<Balance> balances;
+
+  const BalancesTab({
+    super.key,
+    required this.balances,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    if (balances.isEmpty) {
+      return const Center(
+        child: Text('Aucune balance à afficher'),
+      );
+    }
+
+    return ListView.builder(
+      padding: const EdgeInsets.all(16),
+      itemCount: balances.length,
+      itemBuilder: (context, index) {
+        final balance = balances[index];
+        return _buildBalanceCard(context, balance);
+      },
+    );
+  }
+
+  Widget _buildBalanceCard(BuildContext context, Balance balance) {
+    final isDark = Theme.of(context).brightness == Brightness.dark;
+    
+    Color balanceColor;
+    IconData balanceIcon;
+    String balanceText;
+
+    if (balance.shouldReceive) {
+      balanceColor = Colors.green;
+      balanceIcon = Icons.arrow_downward;
+      balanceText = 'À recevoir';
+    } else if (balance.shouldPay) {
+      balanceColor = Colors.red;
+      balanceIcon = Icons.arrow_upward;
+      balanceText = 'À payer';
+    } else {
+      balanceColor = Colors.grey;
+      balanceIcon = Icons.check_circle;
+      balanceText = 'Équilibré';
+    }
+
+    return Card(
+      margin: const EdgeInsets.only(bottom: 12),
+      child: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Row(
+          children: [
+            CircleAvatar(
+              radius: 24,
+              backgroundColor: isDark ? Colors.grey[800] : Colors.grey[200],
+              child: Text(
+                balance.userName.isNotEmpty
+                    ? balance.userName[0].toUpperCase()
+                    : '?',
+                style: const TextStyle(
+                  fontSize: 20,
+                  fontWeight: FontWeight.bold,
+                ),
+              ),
+            ),
+            const SizedBox(width: 16),
+            Expanded(
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  Text(
+                    balance.userName,
+                    style: const TextStyle(
+                      fontSize: 16,
+                      fontWeight: FontWeight.bold,
+                    ),
+                  ),
+                  const SizedBox(height: 4),
+                  Text(
+                    'Payé: ${balance.totalPaid.toStringAsFixed(2)} € • Doit: ${balance.totalOwed.toStringAsFixed(2)} €',
+                    style: TextStyle(
+                      fontSize: 12,
+                      color: isDark ? Colors.grey[400] : Colors.grey[600],
+                    ),
+                  ),
+                ],
+              ),
+            ),
+            Column(
+              crossAxisAlignment: CrossAxisAlignment.end,
+              children: [
+                Row(
+                  children: [
+                    Icon(balanceIcon, size: 16, color: balanceColor),
+                    const SizedBox(width: 4),
+                    Text(
+                      '${balance.absoluteBalance.toStringAsFixed(2)} €',
+                      style: TextStyle(
+                        fontSize: 18,
+                        fontWeight: FontWeight.bold,
+                        color: balanceColor,
+                      ),
+                    ),
+                  ],
+                ),
+                Text(
+                  balanceText,
+                  style: TextStyle(
+                    fontSize: 12,
+                    color: balanceColor,
+                  ),
+                ),
+              ],
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}