feat: 添加用户关注功能

- 新增 Follow 表和 User.bio 字段 (Prisma schema)
- 创建 follow 模块 (action-service-repository)
- 新增 FollowButton/FollowStats/UserList 组件
- 用户页面显示 bio、粉丝/关注数、关注按钮
- 新增 /users/[username]/followers 和 following 页面
- 添加 en-US/zh-CN i18n 翻译

⚠️ 需要运行: prisma migrate dev --name add_follow_and_bio

messages/en-US.json

@@ -354,6 +354,7 @@
     "displayName": "Display Name",
     "notSet": "Not Set",
     "memberSince": "Member Since",
+    "joined": "Joined",
     "logout": "Logout",
     "folders": {
       "title": "Folders",
@@ -364,5 +365,14 @@
       "actions": "Actions",
       "view": "View"
     }
+  },
+  "follow": {
+    "follow": "Follow",
+    "following": "Following",
+    "followers": "Followers",
+    "followersOf": "{username}'s Followers",
+    "followingOf": "{username}'s Following",
+    "noFollowers": "No followers yet",
+    "noFollowing": "Not following anyone yet"
   }
 }

messages/zh-CN.json

@@ -354,6 +354,7 @@
     "displayName": "显示名称",
     "notSet": "未设置",
     "memberSince": "注册时间",
+    "joined": "加入于",
     "logout": "登出",
     "folders": {
       "title": "文件夹",
@@ -364,5 +365,14 @@
       "actions": "操作",
       "view": "查看"
     }
+  },
+  "follow": {
+    "follow": "关注",
+    "following": "已关注",
+    "followers": "粉丝",
+    "followersOf": "{username} 的粉丝",
+    "followingOf": "{username} 的关注",
+    "noFollowers": "还没有粉丝",
+    "noFollowing": "还没有关注任何人"
   }
 }