style(reward): 优化奖励中心金币图标

lib/pages/reward/reward_tasks_view.dart

@@ -149,7 +149,7 @@ class _Balance extends StatelessWidget {
           ),
         ),
         const SizedBox(width: AppDimens.spaceSm),
-        const RewardCoinIcon(size: 32),
+        const RewardCoinIcon(key: Key('reward-balance-coin-icon'), size: 32),
       ],
     );
     if (onOpenWallet == null) return content;

lib/pages/reward/reward_visuals.dart

@@ -7,6 +7,10 @@ import '../../core/theme/app_colors.dart';
 
 const double _coinInnerInsetRatio = 0.1;
 const double _coinLetterRatio = 0.46;
+const double _coinHighlightRatio = 0.18;
+const double _coinHighlightOpacity = 0.54;
+const double _coinLetterShadowBlur = 1.5;
+const double _coinLetterShadowOffset = 0.8;
 const double _taskIconSize = 46;
 const double _taskIconRadius = 12;
 const double _taskGlyphSize = 24;
@@ -20,6 +24,8 @@ const Color _coinOuter = Color(0xFFF6B84E);
 const Color _coinInnerStart = Color(0xFFFFD98B);
 const Color _coinInnerEnd = Color(0xFFE39B31);
 const Color _coinBorder = Color(0xFFFFE0A1);
+const Color _coinHighlight = Color(0xFFFFF4CC);
+const Color _coinLetterShadow = Color(0xFFB66A16);
 const Color _taskIconStart = Color(0xFF4C171E);
 const Color _taskIconEnd = Color(0xFF281014);
 const Color _taskIconSurface = Color(0xFF202022);
@@ -42,8 +48,10 @@ class RewardCoinIcon extends StatelessWidget {
         color: _coinOuter,
         boxShadow: [BoxShadow(color: Color(0x4DF6B84E), blurRadius: 6)],
       ),
-      child: Container(
+      child: Stack(
         alignment: Alignment.center,
+        children: [
+          Container(
             decoration: BoxDecoration(
               shape: BoxShape.circle,
               gradient: const LinearGradient(
@@ -53,15 +61,39 @@ class RewardCoinIcon extends StatelessWidget {
               ),
               border: Border.all(color: _coinBorder),
             ),
-        child: Text(
+          ),
+          Positioned(
+            top: size * 0.12,
+            left: size * 0.18,
+            child: Container(
+              width: size * _coinHighlightRatio,
+              height: size * _coinHighlightRatio,
+              decoration: BoxDecoration(
+                shape: BoxShape.circle,
+                color: _coinHighlight.withValues(alpha: _coinHighlightOpacity),
+              ),
+            ),
+          ),
+          Text(
             'N',
             style: TextStyle(
               color: AppColors.textPrimary,
               fontSize: size * _coinLetterRatio,
               fontWeight: FontWeight.w900,
               height: 1,
+              shadows: const [
+                Shadow(
+                  color: _coinLetterShadow,
+                  blurRadius: _coinLetterShadowBlur,
+                  offset: Offset(
+                    _coinLetterShadowOffset,
+                    _coinLetterShadowOffset,
                   ),
                 ),
+              ],
+            ),
+          ),
+        ],
       ),
     );
   }

test/reward/reward_page_test.dart

@@ -48,6 +48,7 @@ void main() {
     expect(find.byKey(const Key('reward-back-button')), findsOneWidget);
     expect(find.byKey(const Key('reward-help-button')), findsOneWidget);
     expect(find.byKey(const Key('reward-balance')), findsOneWidget);
+    expect(find.byKey(const Key('reward-balance-coin-icon')), findsOneWidget);
     expect(find.byKey(const Key('reward-checkin-card')), findsOneWidget);
     expect(find.byKey(const Key('reward-checkin-action')), findsOneWidget);
     expect(find.byKey(const Key('reward-section-DAILY')), findsOneWidget);