style(dashboard): add theme-responsive borders to cards, lists, and charts

frontend/lib/ui/screens/dashboard/dashboard_screen.dart

@@ -1081,9 +1081,13 @@ class _DashboardScreenState extends ConsumerState<DashboardScreen> {
         decoration: BoxDecoration(
           color: isDark ? AppColors.darkSurfaceCard : Colors.white,
           borderRadius: BorderRadius.circular(12),
+          border: Border.all(
+            color: isDark ? AppColors.darkBorder : AppColors.borderLight,
+            width: 1.0,
+          ),
           boxShadow: [
             BoxShadow(
-              color: Colors.black.withValues(alpha: 0.03),
+              color: Colors.black.withValues(alpha: isDark ? 0.2 : 0.03),
               blurRadius: 10,
               offset: const Offset(0, 4),
             ),
@@ -1102,9 +1106,13 @@ class _DashboardScreenState extends ConsumerState<DashboardScreen> {
       decoration: BoxDecoration(
         color: isDark ? AppColors.darkSurfaceCard : Colors.white,
         borderRadius: BorderRadius.circular(12),
+        border: Border.all(
+          color: isDark ? AppColors.darkBorder : AppColors.borderLight,
+          width: 1.0,
+        ),
         boxShadow: [
           BoxShadow(
-            color: Colors.black.withValues(alpha: 0.03),
+            color: Colors.black.withValues(alpha: isDark ? 0.2 : 0.03),
             blurRadius: 10,
             offset: const Offset(0, 4),
           ),
@@ -1192,9 +1200,13 @@ class _DashboardScreenState extends ConsumerState<DashboardScreen> {
         decoration: BoxDecoration(
           color: isDark ? AppColors.darkSurfaceCard : Colors.white,
           borderRadius: BorderRadius.circular(12),
+          border: Border.all(
+            color: isDark ? AppColors.darkBorder : AppColors.borderLight,
+            width: 1.0,
+          ),
           boxShadow: [
             BoxShadow(
-              color: Colors.black.withValues(alpha: 0.03),
+              color: Colors.black.withValues(alpha: isDark ? 0.2 : 0.03),
               blurRadius: 10,
               offset: const Offset(0, 4),
             ),
@@ -1213,9 +1225,13 @@ class _DashboardScreenState extends ConsumerState<DashboardScreen> {
       decoration: BoxDecoration(
         color: isDark ? AppColors.darkSurfaceCard : Colors.white,
         borderRadius: BorderRadius.circular(12),
+        border: Border.all(
+          color: isDark ? AppColors.darkBorder : AppColors.borderLight,
+          width: 1.0,
+        ),
         boxShadow: [
           BoxShadow(
-            color: Colors.black.withValues(alpha: 0.03),
+            color: Colors.black.withValues(alpha: isDark ? 0.2 : 0.03),
             blurRadius: 10,
             offset: const Offset(0, 4),
           ),

frontend/lib/ui/screens/dashboard/widgets/dashboard_kpis.dart

@@ -286,16 +286,19 @@ class _ChartCard extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final isDark = Theme.of(context).brightness == Brightness.dark;
     return Container(
       padding: const EdgeInsets.all(20),
       decoration: BoxDecoration(
-      color: Theme.of(context).brightness == Brightness.dark
-          ? AppColors.darkSurfaceCard
-          : Colors.white,
+        color: isDark ? AppColors.darkSurfaceCard : Colors.white,
         borderRadius: BorderRadius.circular(16),
+        border: Border.all(
+          color: isDark ? AppColors.darkBorder : AppColors.borderLight,
+          width: 1.0,
+        ),
         boxShadow: [
           BoxShadow(
-            color: Colors.black.withValues(alpha: 0.04),
+            color: Colors.black.withValues(alpha: isDark ? 0.2 : 0.04),
             blurRadius: 12,
             offset: const Offset(0, 4),
           ),
@@ -2534,14 +2537,19 @@ class _KpiSkeleton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final isDark = Theme.of(context).brightness == Brightness.dark;
     return Container(
       height: 120,
       margin: const EdgeInsets.symmetric(vertical: 8),
       decoration: BoxDecoration(
-        color: Theme.of(context).brightness == Brightness.dark
+        color: isDark
             ? AppColors.darkSurfaceCard
             : Colors.grey.shade100,
         borderRadius: BorderRadius.circular(16),
+        border: Border.all(
+          color: isDark ? AppColors.darkBorder : AppColors.borderLight,
+          width: 1.0,
+        ),
       ),
       child: const Center(
         child: CircularProgressIndicator(

frontend/lib/ui/shared/cards/stat_card.dart

@@ -38,9 +38,13 @@ class StatCard extends StatelessWidget {
           decoration: BoxDecoration(
             color: isDark ? AppColors.darkSurfaceCard : Colors.white,
             borderRadius: BorderRadius.circular(12.0),
+            border: Border.all(
+              color: isDark ? AppColors.darkBorder : AppColors.borderLight,
+              width: 1.0,
+            ),
             boxShadow: [
               BoxShadow(
-                color: Colors.black.withValues(alpha: 0.03),
+                color: Colors.black.withValues(alpha: isDark ? 0.2 : 0.03),
                 blurRadius: 8,
                 offset: const Offset(0, 3),
               ),