feat(announcements): add admin/user announcement system

Implements announcements end-to-end (admin CRUD + read status, user list + mark read) with OR-of-AND targeting. Also breaks the ent<->service import cycle by moving schema-facing constants/targeting into a new domain package.

frontend/src/router/index.ts

@@ -187,6 +187,18 @@ const routes: RouteRecordRaw[] = [
       descriptionKey: 'purchase.description'
     }
   },
+  {
+    path: '/announcements',
+    name: 'Announcements',
+    component: () => import('@/views/user/AnnouncementsView.vue'),
+    meta: {
+      requiresAuth: true,
+      requiresAdmin: false,
+      title: 'Announcements',
+      titleKey: 'announcements.title',
+      descriptionKey: 'announcements.description'
+    }
+  },
 
   // ==================== Admin Routes ====================
   {
@@ -265,6 +277,18 @@ const routes: RouteRecordRaw[] = [
       descriptionKey: 'admin.accounts.description'
     }
   },
+  {
+    path: '/admin/announcements',
+    name: 'AdminAnnouncements',
+    component: () => import('@/views/admin/AnnouncementsView.vue'),
+    meta: {
+      requiresAuth: true,
+      requiresAdmin: true,
+      title: 'Announcements',
+      titleKey: 'admin.announcements.title',
+      descriptionKey: 'admin.announcements.description'
+    }
+  },
   {
     path: '/admin/proxies',
     name: 'AdminProxies',