style: fix dark mode theme support by resolving colors from BuildContext

lib/app.dart

@@ -39,9 +39,10 @@ class _YnabAppState extends ConsumerState<YnabApp> {
   @override
   Widget build(BuildContext context) {
     final selectedIndex = ref.watch(_selectedIndexProvider);
+    final theme = Theme.of(context);
+    final colorScheme = theme.colorScheme;
 
     return Scaffold(
-      backgroundColor: kSurfaceBg,
       bottomNavigationBar: NavigationBar(
         selectedIndex: selectedIndex,
         onDestinationSelected: (int index) {
@@ -62,29 +63,29 @@ class _YnabAppState extends ConsumerState<YnabApp> {
             Container(
               padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 12),
               decoration: BoxDecoration(
-                color: kSurfaceBg,
+                color: colorScheme.surface,
                 border: Border(
-                  bottom: BorderSide(color: kDivider, width: 0.5),
+                  bottom: BorderSide(color: colorScheme.outlineVariant, width: 0.5),
                 ),
               ),
               child: Row(
                 children: [
                   Text(
                     _navItems[selectedIndex].label,
-                    style: const TextStyle(
-                      color: kTextPrimary,
+                    style: TextStyle(
+                      color: colorScheme.onSurface,
                       fontSize: 18,
                       fontWeight: FontWeight.w600,
                     ),
                   ),
                   const Spacer(),
                   IconButton(
-                    icon: const Icon(Icons.add, color: kGreenAccent),
+                    icon: Icon(Icons.add, color: colorScheme.primary),
                     onPressed: () {},
                     tooltip: 'Ajouter une transaction',
                   ),
                   IconButton(
-                    icon: const Icon(Icons.search, color: kTextSecondary),
+                    icon: Icon(Icons.search, color: colorScheme.onSurfaceVariant),
                     onPressed: () {},
                     tooltip: 'Rechercher',
                   ),

lib/screens/accounts_screen.dart

@@ -54,10 +54,10 @@ class _AccountCard extends StatelessWidget {
               width: 44,
               height: 44,
               decoration: BoxDecoration(
-                color: kSurfaceElevated,
+                color: Theme.of(context).colorScheme.primaryContainer,
                 borderRadius: BorderRadius.circular(12),
               ),
-              child: Icon(_icon(), color: kTextSecondary, size: 22),
+              child: Icon(_icon(), color: Theme.of(context).colorScheme.onSurfaceVariant, size: 22),
             ),
             const SizedBox(width: 14),
             Expanded(
@@ -78,7 +78,7 @@ class _AccountCard extends StatelessWidget {
               formatCurrency(account.balance),
               style: Theme.of(context).textTheme.titleMedium?.copyWith(
                     fontWeight: FontWeight.w700,
-                    color: account.balance >= 0 ? kGreenAccent : kRedAccent,
+                    color: account.balance >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
                   ),
             ),
           ],

lib/screens/budget_screen.dart

@@ -62,7 +62,7 @@ class _CategoryGroupTile extends ConsumerWidget {
                 Icon(
                   expanded ? Icons.keyboard_arrow_down : Icons.keyboard_arrow_right,
                   size: 18,
-                  color: kTextSecondary,
+                  color: Theme.of(context).colorScheme.onSurfaceVariant,
                 ),
                 const SizedBox(width: 8),
                 Text(group.name,
@@ -124,7 +124,7 @@ class _CategoryRow extends ConsumerWidget {
                     formatCurrency(remaining),
                     style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                           fontWeight: FontWeight.w600,
-                          color: remaining >= 0 ? kGreenAccent : kRedAccent,
+                          color: remaining >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
                         ),
                   ),
                 ],
@@ -134,9 +134,9 @@ class _CategoryRow extends ConsumerWidget {
                 borderRadius: BorderRadius.circular(4),
                 child: LinearProgressIndicator(
                   value: pct,
-                  backgroundColor: kDivider,
+                  backgroundColor: Theme.of(context).colorScheme.outlineVariant,
                   valueColor: AlwaysStoppedAnimation<Color>(
-                    remaining >= 0 ? kGreenAccent : kRedAccent,
+                    remaining >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
                   ),
                   minHeight: 4,
                 ),

lib/screens/dashboard_screen.dart

@@ -72,7 +72,7 @@ class _BalanceCard extends StatelessWidget {
               style: Theme.of(context).textTheme.headlineLarge?.copyWith(
                     fontSize: 36,
                     fontWeight: FontWeight.w700,
-                    color: balance >= 0 ? kGreenAccent : kRedAccent,
+                    color: balance >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
                   ),
             ),
           ],
@@ -101,13 +101,13 @@ class _AccountMiniCard extends StatelessWidget {
       margin: const EdgeInsets.only(bottom: 6),
       child: ListTile(
         dense: true,
-        leading: Icon(_icon(), color: kTextSecondary),
+        leading: Icon(_icon(), color: Theme.of(context).colorScheme.onSurfaceVariant),
         title: Text(account.name, style: Theme.of(context).textTheme.bodyMedium),
         trailing: Text(
           formatCurrency(account.balance),
           style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                 fontWeight: FontWeight.w600,
-                color: account.balance >= 0 ? kGreenAccent : kRedAccent,
+                color: account.balance >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
               ),
         ),
       ),
@@ -127,11 +127,11 @@ class _TxItem extends StatelessWidget {
         dense: true,
         leading: CircleAvatar(
           radius: 18,
-          backgroundColor: kSurfaceElevated,
+          backgroundColor: Theme.of(context).colorScheme.primaryContainer,
           child: Icon(
             transaction.amount >= 0 ? Icons.arrow_downward : Icons.arrow_upward,
             size: 16,
-            color: transaction.amount >= 0 ? kGreenAccent : kRedAccent,
+            color: transaction.amount >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
           ),
         ),
         title: Text(transaction.payee, style: Theme.of(context).textTheme.bodyMedium),
@@ -143,7 +143,7 @@ class _TxItem extends StatelessWidget {
           formatCurrency(transaction.amount),
           style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                 fontWeight: FontWeight.w600,
-                color: transaction.amount >= 0 ? kGreenAccent : kRedAccent,
+                        color: transaction.amount >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
               ),
         ),
       ),

lib/screens/transactions_screen.dart

@@ -22,11 +22,11 @@ class TransactionsScreen extends ConsumerWidget {
             dense: true,
             leading: CircleAvatar(
               radius: 18,
-              backgroundColor: kSurfaceElevated,
+              backgroundColor: Theme.of(context).colorScheme.primaryContainer,
               child: Icon(
                 t.amount >= 0 ? Icons.arrow_downward : Icons.arrow_upward,
                 size: 16,
-                color: t.amount >= 0 ? kGreenAccent : kRedAccent,
+                color: t.amount >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
               ),
             ),
             title: Text(t.payee, style: Theme.of(context).textTheme.bodyMedium),
@@ -42,7 +42,7 @@ class TransactionsScreen extends ConsumerWidget {
                   formatCurrency(t.amount),
                   style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                         fontWeight: FontWeight.w600,
-                        color: t.amount >= 0 ? kGreenAccent : kRedAccent,
+                        color: t.amount >= 0 ? Theme.of(context).colorScheme.primary : Theme.of(context).colorScheme.error,
                       ),
                 ),
               ],

lib/theme/app_theme.dart

@@ -133,6 +133,14 @@ final ThemeData ynabDarkTheme = ThemeData(
     seedColor: const Color(0xFFCAD8C3),
     brightness: Brightness.dark,
   ),
+  cardTheme: CardThemeData(
+    elevation: 0,
+    shape: RoundedRectangleBorder(
+      borderRadius: BorderRadius.circular(12),
+      side: const BorderSide(color: Color(0xFF43493E), width: 1),
+    ),
+    clipBehavior: Clip.antiAlias,
+  ),
 );
 
 // Utils