Add headless CMS for official site content management

Integrate article and page management into the Laravel admin dashboard
to serve as a headless CMS for the Next.js frontend (usher-site).

Backend:
- 7 migrations: article_categories, article_tags, articles, pivots, attachments, pages
- 5 models with relationships: Article, ArticleCategory, ArticleTag, ArticleAttachment, Page
- 4 admin controllers: articles (with publish/archive/pin), categories, tags, pages
- Admin views with EasyMDE markdown editor, multi-select categories/tags
- Navigation section "官網管理" in admin sidebar

API (v1):
- GET /api/v1/articles (filtered by type, category, tag, search; paginated)
- GET /api/v1/articles/{slug} (with related articles)
- GET /api/v1/categories
- GET /api/v1/pages/{slug} (with children)
- GET /api/v1/homepage (aggregated homepage data)
- Attachment download endpoint
- CORS configured for usher.org.tw, vercel.app, localhost:3000

Content migration:
- ImportHugoContent command: imports Hugo markdown files as articles/pages
- Successfully imported 27 articles, 17 categories, 11 tags, 9 pages

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

routes/api.php

@@ -1,5 +1,8 @@
 <?php
 
+use App\Http\Controllers\Api\ArticleController;
+use App\Http\Controllers\Api\HomepageController;
+use App\Http\Controllers\Api\PageController;
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Route;
 
@@ -17,3 +20,28 @@ use Illuminate\Support\Facades\Route;
 Route::middleware('auth:sanctum')->get('/user', function (Request $request) {
     return $request->user();
 });
+
+// Public API v1
+Route::prefix('v1')->group(function () {
+    // Articles
+    Route::get('/articles', [ArticleController::class, 'index']);
+    Route::get('/articles/{slug}', [ArticleController::class, 'show']);
+    Route::get('/articles/{slug}/attachments/{id}/download', [ArticleController::class, 'downloadAttachment']);
+
+    // Categories
+    Route::get('/categories', function () {
+        $categories = \App\Models\ArticleCategory::withCount(['articles' => function ($q) {
+            $q->active()->forAccessLevel();
+        }])
+            ->orderBy('sort_order')
+            ->get();
+
+        return \App\Http\Resources\CategoryResource::collection($categories);
+    });
+
+    // Pages
+    Route::get('/pages/{slug}', [PageController::class, 'show']);
+
+    // Homepage
+    Route::get('/homepage', [HomepageController::class, 'index']);
+});