feat: Phase 1c — Platform Admin Dashboard

Full super-admin dashboard for SaaS platform management:

Backend (10 files):
- Migration 003: Add is_super_admin column to users table
- JWT Claims: Carry is_super_admin through access tokens
- SuperAdmin extractor: Axum FromRequestParts that rejects non-admins (403)
- Admin API module: 10 endpoints behind /api/admin/*
  - GET /stats (KPIs: licenses, users, MRR, servers, signups)
  - GET/POST /licenses (paginated, filterable, manual generation)
  - GET/PATCH /licenses/:id (detail view, revoke/activate)
  - GET /subscriptions (module sub list with MRR breakdown)
  - GET/PATCH /users (paginated, toggle admin, disable accounts)
  - GET /servers (fleet overview across all licenses)
  - GET /health (DB pool, NATS status, table row counts)
- Bootstrap updated: first user gets is_super_admin = true

Frontend (8 files):
- 5 admin views in src/views/platform-admin/
- DashboardLayout: "Platform" nav section (gated on isSuperAdmin)
- Router: /admin/* routes with superAdmin meta guard
- Auth store: isSuperAdmin computed property
- Types: is_super_admin on User interface

Build: 80 chunks, zero TS errors, clean production build.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/router/index.ts

@@ -113,6 +113,37 @@ const routes: RouteRecordRaw[] = [
         name: 'settings',
         component: () => import('@/views/admin/SettingsView.vue'),
       },
+      // Platform Admin views (super-admin only, guarded in components)
+      {
+        path: 'admin',
+        name: 'platform-admin',
+        component: () => import('@/views/platform-admin/AdminDashboard.vue'),
+        meta: { superAdmin: true },
+      },
+      {
+        path: 'admin/licenses',
+        name: 'platform-licenses',
+        component: () => import('@/views/platform-admin/AdminLicenses.vue'),
+        meta: { superAdmin: true },
+      },
+      {
+        path: 'admin/subscriptions',
+        name: 'platform-subscriptions',
+        component: () => import('@/views/platform-admin/AdminSubscriptions.vue'),
+        meta: { superAdmin: true },
+      },
+      {
+        path: 'admin/users',
+        name: 'platform-users',
+        component: () => import('@/views/platform-admin/AdminUsers.vue'),
+        meta: { superAdmin: true },
+      },
+      {
+        path: 'admin/servers',
+        name: 'platform-servers',
+        component: () => import('@/views/platform-admin/AdminServers.vue'),
+        meta: { superAdmin: true },
+      },
     ],
   },
 
@@ -191,6 +222,8 @@ router.beforeEach((to, _from, next) => {
 
   if (to.meta.requiresAuth && !auth.isAuthenticated) {
     next({ name: 'login', query: { redirect: to.fullPath } })
+  } else if (to.meta.superAdmin && !auth.isSuperAdmin) {
+    next({ name: 'dashboard' })
   } else if (to.meta.guest && auth.isAuthenticated) {
     next({ name: 'dashboard' })
   } else {