chore(站内信): 消息页、后台空壳页、两个接口和 message 表一起下线

历史上一共 6 条站内信（最后一条 2025-06），发信接口两代前端都没接过，后台页面只有一句
「未完待续」，OJ2 顶栏也没有入口。

0033 是 DROP TABLE，部署要显式放行：OJ2_ALLOW_DESTRUCTIVE=1 docker/deploy.sh，
或 CI 手工触发时勾 allow_destructive。

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/src/routes.ts

@@ -111,11 +111,6 @@ export const ojs: RouteRecordRaw = {
       component: () => import("oj/achievement/index.vue"),
       meta: { requiresAuth: true },
     },
-    {
-      path: "message",
-      component: () => import("oj/user/message.vue"),
-      meta: { requiresAuth: true },
-    },
     {
       path: "learn",
       name: "learn home",
@@ -268,12 +263,6 @@ export const admins: RouteRecordRaw = {
       props: true,
       meta: { requiresSuperAdmin: true },
     },
-    {
-      path: "message/list",
-      name: "admin message list",
-      component: () => import("admin/communication/messages.vue"),
-      meta: { requiresSuperAdmin: true },
-    },
     {
       path: "tutorial/list",
       name: "admin tutorial list",