feat(i18n): 全面实现应用核心功能模块的国际化支持

- 新增 i18n 翻译资源，覆盖睡眠、饮水、体重、锻炼、用药 AI 识别、步数、健身圆环、基础代谢及设置等核心模块
- 重构相关页面及组件（如 SleepDetail, WaterDetail, WorkoutHistory 等）使用 `useI18n` 钩子替换硬编码文本
- 升级 `utils/date` 工具库与 `DateSelector` 组件，支持基于语言环境的日期格式化与显示
- 完善登录页、注销流程及权限申请弹窗的双语提示信息
- 优化部分页面的 UI 细节与字体样式以适配多语言显示

app/(tabs)/challenges.tsx

@@ -602,14 +602,14 @@ const styles = StyleSheet.create({
     marginBottom: 26,
   },
   title: {
-    fontSize: 32,
+    fontSize: 28,
     fontWeight: '700',
     letterSpacing: 1,
     fontFamily: 'AliBold'
   },
   subtitle: {
     marginTop: 6,
-    fontSize: 14,
+    fontSize: 12,
     fontWeight: '500',
     opacity: 0.8,
     fontFamily: 'AliRegular'
@@ -619,8 +619,8 @@ const styles = StyleSheet.create({
     alignItems: 'center',
   },
   joinButtonGlass: {
-    paddingHorizontal: 16,
-    paddingVertical: 10,
+    paddingHorizontal: 14,
+    paddingVertical: 8,
     borderRadius: 16,
     minWidth: 70,
     alignItems: 'center',
@@ -629,7 +629,7 @@ const styles = StyleSheet.create({
     borderColor: 'rgba(255,255,255,0.45)',
   },
   joinButtonLabel: {
-    fontSize: 14,
+    fontSize: 12,
     fontWeight: '700',
     color: '#0f1528',
     letterSpacing: 0.5,
@@ -639,8 +639,8 @@ const styles = StyleSheet.create({
     backgroundColor: 'rgba(255,255,255,0.7)',
   },
   createButton: {
-    width: 40,
-    height: 40,
+    width: 36,
+    height: 36,
     borderRadius: 20,
     alignItems: 'center',
     justifyContent: 'center',