feat: Implement account management center with authentication and subscription features, supported by new backend, i18n, and Supabase integration.

frontend/lib/i18n.ts

@@ -114,12 +114,14 @@ const MESSAGES: Record<Locale, Record<string, string>> = {
     "account.subtitle": "查看身份、权限与 Bot 绑定信息",
     "account.backDashboard": "返回看板",
     "account.refresh": "刷新",
+    "account.signIn": "登录 / 注册",
     "account.signOut": "退出登录",
     "account.loading": "正在同步账户信息...",
     "account.error": "加载失败: {message}",
     "account.updatedAt": "最近同步: {time}",
     "account.guestName": "PolyWeather 用户",
     "account.authenticated": "已登录",
+    "account.guest": "游客模式",
     "account.subscriptionActive": "订阅有效",
     "account.subscriptionRequired": "需要订阅",
     "account.subscriptionUnknown": "订阅状态未知",
@@ -138,6 +140,8 @@ const MESSAGES: Record<Locale, Record<string, string>> = {
     "account.field.bindCommand": "绑定命令",
     "account.field.bindHint":
       "将下面命令发送到 Telegram Bot，可把网页账户与机器人权限绑定。",
+    "account.mode.supabaseRequired": "Supabase 强制登录",
+    "account.mode.supabaseOptional": "Supabase 可选登录",
     "account.mode.supabase": "Supabase 会话鉴权",
     "account.mode.legacy": "Legacy Token 鉴权",
     "account.mode.disabled": "未启用权限校验",
@@ -266,12 +270,14 @@ const MESSAGES: Record<Locale, Record<string, string>> = {
     "account.subtitle": "Review identity, access status, and bot binding info",
     "account.backDashboard": "Back to Dashboard",
     "account.refresh": "Refresh",
+    "account.signIn": "Sign in / Sign up",
     "account.signOut": "Sign out",
     "account.loading": "Syncing account snapshot...",
     "account.error": "Failed to load: {message}",
     "account.updatedAt": "Last synced: {time}",
     "account.guestName": "PolyWeather User",
     "account.authenticated": "Authenticated",
+    "account.guest": "Guest Mode",
     "account.subscriptionActive": "Subscription active",
     "account.subscriptionRequired": "Subscription required",
     "account.subscriptionUnknown": "Subscription unknown",
@@ -290,6 +296,8 @@ const MESSAGES: Record<Locale, Record<string, string>> = {
     "account.field.bindCommand": "Binding command",
     "account.field.bindHint":
       "Send this command to the Telegram bot to bind web account identity.",
+    "account.mode.supabaseRequired": "Supabase required auth",
+    "account.mode.supabaseOptional": "Supabase optional auth",
     "account.mode.supabase": "Supabase session auth",
     "account.mode.legacy": "Legacy token auth",
     "account.mode.disabled": "Auth guard disabled",