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>

app/Http/Controllers/Api/HomepageController.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace App\Http\Controllers\Api;
+
+use App\Http\Controllers\Controller;
+use App\Http\Resources\ArticleCollectionResource;
+use App\Http\Resources\CategoryResource;
+use App\Http\Resources\PageResource;
+use App\Models\Article;
+use App\Models\ArticleCategory;
+use App\Models\Page;
+
+class HomepageController extends Controller
+{
+    public function index()
+    {
+        // Featured/pinned articles
+        $featured = Article::with(['categories', 'tags'])
+            ->active()
+            ->forAccessLevel()
+            ->pinned()
+            ->orderBy('display_order')
+            ->limit(5)
+            ->get();
+
+        // Latest articles by type
+        $latestBlog = Article::with(['categories'])
+            ->active()
+            ->forAccessLevel()
+            ->byContentType('blog')
+            ->orderByDesc('published_at')
+            ->limit(6)
+            ->get();
+
+        $latestNotice = Article::with(['categories'])
+            ->active()
+            ->forAccessLevel()
+            ->byContentType('notice')
+            ->orderByDesc('published_at')
+            ->limit(4)
+            ->get();
+
+        $latestDocument = Article::with(['categories'])
+            ->active()
+            ->forAccessLevel()
+            ->byContentType('document')
+            ->orderByDesc('published_at')
+            ->limit(4)
+            ->get();
+
+        $latestRelatedNews = Article::with(['categories'])
+            ->active()
+            ->forAccessLevel()
+            ->byContentType('related_news')
+            ->orderByDesc('published_at')
+            ->limit(4)
+            ->get();
+
+        // About page
+        $aboutPage = Page::published()
+            ->where('slug', 'about')
+            ->first();
+
+        // Categories
+        $categories = ArticleCategory::withCount(['articles' => function ($q) {
+            $q->active()->forAccessLevel();
+        }])
+            ->orderBy('sort_order')
+            ->get();
+
+        return response()->json([
+            'featured' => ArticleCollectionResource::collection($featured),
+            'latest_blog' => ArticleCollectionResource::collection($latestBlog),
+            'latest_notice' => ArticleCollectionResource::collection($latestNotice),
+            'latest_document' => ArticleCollectionResource::collection($latestDocument),
+            'latest_related_news' => ArticleCollectionResource::collection($latestRelatedNews),
+            'about' => $aboutPage ? new PageResource($aboutPage) : null,
+            'categories' => CategoryResource::collection($categories),
+        ]);
+    }
+}