feat: implement dynamic theme palette selection

- Introduced a new feature allowing users to select from multiple accent color palettes for buttons, cards, and chat bubbles.
- Added `AppThemePalette` provider to manage the current theme palette and persist user selections.
- Updated the `AppTheme` class to utilize the selected palette for light and dark themes, enhancing visual customization.
- Enhanced the `AppCustomizationPage` to include a palette selector, improving user experience and personalization options.
- Updated localization files to support new palette selection UI elements in multiple languages.

lib/shared/widgets/loading_states.dart

@@ -21,7 +21,7 @@ class ConduitLoading {
   }) {
     return _LoadingIndicator(
       size: size,
-      color: color ?? BrandService.primaryBrandColor,
+      color: color,
       message: message,
       type: _LoadingType.primary,
     );
@@ -40,7 +40,7 @@ class ConduitLoading {
           color ??
           (context?.conduitTheme.loadingIndicator ??
               context?.conduitTheme.buttonPrimary ??
-              AppTheme.brandPrimary),
+              BrandService.primaryBrandColor(context: context)),
       message: message,
       type: _LoadingType.inline,
     );
@@ -91,30 +91,35 @@ enum _LoadingType { primary, inline, button }
 
 class _LoadingIndicator extends StatelessWidget {
   final double size;
-  final Color color;
+  final Color? color;
   final String? message;
   final _LoadingType type;
 
   const _LoadingIndicator({
     required this.size,
-    required this.color,
+    this.color,
     this.message,
     required this.type,
   });
 
   @override
   Widget build(BuildContext context) {
+    final resolvedColor = color ?? context.conduitTheme.loadingIndicator;
+
     Widget indicator;
 
     if (Platform.isIOS) {
-      indicator = CupertinoActivityIndicator(color: color, radius: size / 2);
+      indicator = CupertinoActivityIndicator(
+        color: resolvedColor,
+        radius: size / 2,
+      );
     } else {
       indicator = SizedBox(
         width: size,
         height: size,
         child: CircularProgressIndicator(
           strokeWidth: size / 8,
-          valueColor: AlwaysStoppedAnimation<Color>(color),
+          valueColor: AlwaysStoppedAnimation<Color>(resolvedColor),
         ),
       );
     }