Add admin command menu, mobile drawer and animated course progress

- cmdk 1.1.1: Cmd/Ctrl+K command menu in the admin panel (students,
  courses, lessons, admin sections) plus a "Search" button in the sidebar.
  New read-only endpoint GET /api/admin/search with the same admin role
  check as /api/admin/export-users; query length 2-100 chars.
- vaul 1.1.2: ResponsiveDialog wrapper (Base UI Dialog on desktop, bottom
  drawer below 768px) styled per DS-2. Used for the storefront checkout on
  the dashboard and for course navigation on phones (tablet and desktop
  unchanged).
- @number-flow/react 0.6.2: animated "N of M lessons" and completion
  percent in course navigation; respects prefers-reduced-motion.

No migrations. Not deployed.

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

package.json

@@ -21,6 +21,7 @@
     "@dnd-kit/sortable": "^10.0.0",
     "@dnd-kit/utilities": "^3.2.2",
     "@kinescope/react-kinescope-player": "^0.5.4",
+    "@number-flow/react": "^0.6.2",
     "@prisma/adapter-pg": "^7.6.0",
     "@prisma/client": "^7.6.0",
     "@tiptap/extension-image": "^3.22.2",
@@ -34,6 +35,7 @@
     "better-auth": "^1.6.0",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
+    "cmdk": "^1.1.1",
     "defuddle": "^0.19.1",
     "disposable-email-domains": "^1.0.62",
     "force-graph": "^1.51.4",
@@ -55,6 +57,7 @@
     "sonner": "^2.0.7",
     "tailwind-merge": "^3.5.0",
     "unified": "^11.0.5",
+    "vaul": "^1.1.2",
     "zod": "^4.3.6"
   },
   "devDependencies": {