feat(shared): legacy presentation/ + shared design system + widgets

- lib/presentation : pages legacy (explore/network, notifications) avec BLoC
- lib/shared/design_system : UnionFlow Design System v2 (tokens, components)
  + MD3 tokens + module_colors par feature
- lib/shared/widgets : widgets transversaux (core_card, core_shimmer,
  error_widget, loading_widget, powered_by_lions_dev, etc.)
- lib/shared/constants + utils

lib/shared/widgets/action_row.dart

@@ -33,7 +33,7 @@ class ActionRow extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final isDark = Theme.of(context).brightness == Brightness.dark;
-    final iconColor = isDark ? AppColors.textSecondaryDark : AppColors.textSecondaryLight;
+    final iconColor = isDark ? AppColors.textSecondaryDark : AppColors.textSecondary;
 
     return Padding(
       padding: const EdgeInsets.only(top: 8.0),
@@ -75,18 +75,18 @@ class ActionRow extends StatelessWidget {
               child: Container(
                 padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 4),
                 decoration: BoxDecoration(
-                  color: AppColors.primaryGreen.withOpacity(0.1),
+                  color: AppColors.primary.withOpacity(0.1),
                   borderRadius: BorderRadius.circular(12),
                 ),
                 child: Row(
                   children: [
                     if (customActionIcon != null) ...[
-                      Icon(customActionIcon, size: 14, color: AppColors.primaryGreen),
+                      Icon(customActionIcon, size: 14, color: AppColors.primary),
                       const SizedBox(width: 4),
                     ],
                     Text(
                       customActionLabel ?? '',
-                      style: AppTypography.badgeText.copyWith(color: AppColors.primaryGreen),
+                      style: AppTypography.badgeText.copyWith(color: AppColors.primary),
                     ),
                   ],
                 ),