feat(ui): 增加视觉 token 与统一导航

lib/core/theme/app_colors.dart

@@ -20,6 +20,9 @@ abstract final class AppColors {
   /// Coins, rewards, and the playback progress line.
   static const gold = Color(0xFFF6C453);
 
+  /// Favorite/like heart without competing with the chili primary action.
+  static const favorite = Color(0xFFD74A7D);
+
   /// Text placed on [gold].
   static const onGold = Color(0xFF2A1810);
 

lib/core/theme/app_dimens.dart

@@ -0,0 +1,40 @@
+// Author: fruit.com.cn
+
+/// K20 cross-page spacing, type, radius, and control sizes.
+abstract final class AppDimens {
+  static const double spaceXs = 4;
+  static const double spaceSm = 8;
+  static const double spaceMd = 12;
+  static const double spaceLg = 16;
+  static const double spaceXl = 24;
+
+  static const double pageHorizontal = 16;
+  static const double cardRadius = 16;
+  static const double cardPadding = 16;
+  static const double innerRadius = 12;
+  static const double innerPadding = 12;
+  static const double pillRadius = 20;
+
+  static const double caption = 12;
+  static const double body = 14;
+  static const double listTitle = 15;
+  static const double sectionTitle = 16;
+  static const double pageTitle = 20;
+  static const double detailHeadline = 24;
+  static const double navLabel = 11;
+
+  static const double buttonHeight = 48;
+  static const double primaryButtonHeight = 52;
+  static const double tapTarget = 44;
+
+  static const double navHeight = 64;
+  static const double navIcon = 22;
+  static const double progressHeight = 4;
+  static const double progressRadius = 4;
+
+  static const double accountCardHeight = 64;
+  static const double accountIcon = 18;
+  static const double accountLabel = 11;
+
+  static const double watchPlaceholderHeight = 114;
+}

lib/core/theme/app_theme.dart

@@ -1,8 +1,10 @@
 // Author: fruit.com.cn
 
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 
 import 'app_colors.dart';
+import 'app_dimens.dart';
 
 /// Light paper and warm-cocoa themes for the Indonesia evening palette.
 abstract final class AppTheme {
@@ -80,6 +82,32 @@ abstract final class AppTheme {
         style: ButtonStyle(
           backgroundColor: WidgetStateProperty.resolveWith(_buttonColor),
           foregroundColor: const WidgetStatePropertyAll(AppColors.onPrimary),
+          minimumSize: const WidgetStatePropertyAll(
+            Size(0, AppDimens.buttonHeight),
+          ),
+        ),
+      ),
+      outlinedButtonTheme: OutlinedButtonThemeData(
+        style: ButtonStyle(
+          foregroundColor: WidgetStatePropertyAll(
+            dark ? AppColors.blueSoft : AppColors.bluePressed,
+          ),
+          minimumSize: const WidgetStatePropertyAll(
+            Size(0, AppDimens.buttonHeight),
+          ),
+          side: WidgetStatePropertyAll(
+            BorderSide(
+              color: dark ? AppColors.outlineDark : AppColors.outlineLight,
+            ),
+          ),
+        ),
+      ),
+      appBarTheme: const AppBarTheme(
+        systemOverlayStyle: SystemUiOverlayStyle.light,
+        titleTextStyle: TextStyle(
+          color: AppColors.cream,
+          fontSize: AppDimens.pageTitle,
+          fontWeight: FontWeight.w800,
         ),
       ),
       switchTheme: SwitchThemeData(

lib/core/widgets/app_bottom_nav.dart

@@ -0,0 +1,109 @@
+// Author: fruit.com.cn
+
+import 'package:flutter/material.dart';
+
+import '../theme/app_colors.dart';
+import '../theme/app_dimens.dart';
+
+/// One destination rendered by [AppBottomNav].
+class AppBottomNavItem {
+  const AppBottomNavItem({
+    required this.tabKey,
+    required this.icon,
+    required this.selectedIcon,
+    required this.label,
+    required this.onTap,
+    this.selected = false,
+  });
+
+  final Key tabKey;
+  final IconData icon;
+  final IconData selectedIcon;
+  final String label;
+  final VoidCallback onTap;
+  final bool selected;
+}
+
+/// Shared bottom navigation used by all root tabs and the player fallback.
+class AppBottomNav extends StatelessWidget {
+  const AppBottomNav({
+    super.key,
+    required this.items,
+    this.backgroundColor = AppColors.bar,
+  });
+
+  final List<AppBottomNavItem> items;
+  final Color backgroundColor;
+
+  @override
+  Widget build(BuildContext context) => SafeArea(
+    top: false,
+    child: Container(
+      height: AppDimens.navHeight,
+      decoration: BoxDecoration(
+        color: backgroundColor,
+        border: const Border(
+          top: BorderSide(color: AppColors.outlineVariantDark),
+        ),
+      ),
+      child: Row(
+        children: [for (final item in items) _NavDestination(item: item)],
+      ),
+    ),
+  );
+}
+
+class _NavDestination extends StatelessWidget {
+  const _NavDestination({required this.item});
+
+  final AppBottomNavItem item;
+
+  @override
+  Widget build(BuildContext context) => Expanded(
+    child: Semantics(
+      button: true,
+      selected: item.selected,
+      label: item.label,
+      child: InkWell(
+        key: item.tabKey,
+        onTap: item.onTap,
+        child: ConstrainedBox(
+          constraints: const BoxConstraints(minHeight: AppDimens.tapTarget),
+          child: Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            children: [
+              AnimatedContainer(
+                duration: const Duration(milliseconds: 160),
+                curve: Curves.easeOut,
+                padding: const EdgeInsets.symmetric(
+                  horizontal: 14,
+                  vertical: 3,
+                ),
+                decoration: BoxDecoration(
+                  color: item.selected ? AppColors.blue : Colors.transparent,
+                  borderRadius: BorderRadius.circular(14),
+                ),
+                child: Icon(
+                  item.selected ? item.selectedIcon : item.icon,
+                  size: AppDimens.navIcon,
+                  color: item.selected ? AppColors.onPrimary : AppColors.muted,
+                ),
+              ),
+              const SizedBox(height: 2),
+              Text(
+                item.label,
+                maxLines: 1,
+                overflow: TextOverflow.ellipsis,
+                style: TextStyle(
+                  fontSize: AppDimens.navLabel,
+                  fontWeight: item.selected ? FontWeight.w700 : FontWeight.w500,
+                  color: item.selected ? AppColors.blueSoft : AppColors.muted,
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    ),
+  );
+}