feat(life): replace multiple tags with single category for posts

Add default category support and enforce one category per Life Post
Update UI filters, forms, and translations to reflect category semantics

system-wordings.ts

@@ -449,12 +449,12 @@ export const systemWordingMessages = {
         bodyLabel: 'Post',
         bodyPlaceholder: 'Share a thought, tip, or discovery...',
         newPost: 'New Post',
-        tags: 'Tags',
+        category: 'Category',
         languages: 'Languages',
         allLanguages: 'All languages',
-        allTags: 'All',
-        tagPlaceholder: 'Select tags',
-        searchTags: 'Search tags',
+        allCategories: 'All',
+        categoryPlaceholder: 'Select category',
+        searchCategories: 'Search categories',
         search: 'Search Life',
         searchPlaceholder: 'Search post content...',
         clearSearch: 'Clear search',
@@ -512,7 +512,7 @@ export const systemWordingMessages = {
         saveFailed: 'Save failed',
         deleteFailed: 'Delete failed',
         bodyRequired: 'Please enter a post.',
-        tagRequired: 'Please select at least one tag.',
+        categoryRequired: 'Please select a category.',
         byUnknown: 'Community member',
         edited: 'Edited',
         deleteConfirm: 'Delete this post?',
@@ -555,6 +555,7 @@ export const systemWordingMessages = {
         languageName: 'Language name',
         enabled: 'Enabled',
         defaultLanguage: 'Default language',
+        defaultCategory: 'Default category',
         sortOrder: 'Sort order',
         newLanguage: 'New language',
         editLanguage: 'Edit language',
@@ -620,7 +621,7 @@ export const systemWordingMessages = {
       itemUsages: 'Item usages',
       acquisitionMethods: 'Acquisition methods',
       maps: 'Maps',
-      lifeTags: 'Life tags'
+      lifeCategories: 'Life categories'
     },
     appearance: {
       time: 'Time',
@@ -763,7 +764,8 @@ export const systemWordingMessages = {
       taskDoesNotExist: 'Task does not exist',
       postRequired: 'Please enter a post',
       postTooLong: 'Post is too long',
-      lifeTagRequired: 'Please select at least one tag',
+      lifeCategoryRequired: 'Please select a category',
+      lifeCategoryInvalid: 'Category is invalid',
       commentRequired: 'Please enter a comment',
       commentTooLong: 'Comment is too long',
       reactionInvalid: 'Reaction is invalid',
@@ -1270,12 +1272,12 @@ export const systemWordingMessages = {
         bodyLabel: '动态内容',
         bodyPlaceholder: '分享一段想法、心得或发现……',
         newPost: 'New Post',
-        tags: '标签',
+        category: 'Category',
         languages: '语言区',
         allLanguages: '全部语言',
-        allTags: '全部',
-        tagPlaceholder: '选择标签',
-        searchTags: '搜索标签',
+        allCategories: '全部',
+        categoryPlaceholder: '选择 Category',
+        searchCategories: '搜索 Category',
         search: '搜索动态',
         searchPlaceholder: '搜索动态内容……',
         clearSearch: '清除搜索',
@@ -1333,7 +1335,7 @@ export const systemWordingMessages = {
         saveFailed: '保存失败',
         deleteFailed: '删除失败',
         bodyRequired: '请输入动态内容。',
-        tagRequired: '请至少选择 1 个标签。',
+        categoryRequired: '请选择 Category。',
         byUnknown: '社区成员',
         edited: '已编辑',
         deleteConfirm: '确认删除这条动态？',
@@ -1376,6 +1378,7 @@ export const systemWordingMessages = {
         languageName: '语言名称',
         enabled: '启用',
         defaultLanguage: '默认语言',
+        defaultCategory: '默认 Category',
         sortOrder: '排序',
         newLanguage: '新增语言',
         editLanguage: '编辑语言',
@@ -1441,7 +1444,7 @@ export const systemWordingMessages = {
       itemUsages: '物品用途',
       acquisitionMethods: '入手方式',
       maps: '地图',
-      lifeTags: 'Life 标签'
+      lifeCategories: 'Life Categories'
     },
     appearance: {
       time: '时段',
@@ -1584,7 +1587,8 @@ export const systemWordingMessages = {
         taskDoesNotExist: '任务不存在',
         postRequired: '请输入动态内容',
         postTooLong: '动态内容过长',
-        lifeTagRequired: '请至少选择 1 个标签',
+        lifeCategoryRequired: '请选择 Category',
+        lifeCategoryInvalid: 'Category 不合法',
         commentRequired: '请输入评论内容',
         commentTooLong: '评论内容过长',
         reactionInvalid: '互动类型不合法',