feat: 插件使用说明（usage）+ 页面缓存命中统计

- plugin.json 新增 usage 字段（多行文本），后台插件卡片折叠展示；四个内置插件补齐使用说明
- PageCacheMiddleware 记录命中/未命中计数（按日滚动），仪表盘新增「页面缓存」统计卡（条目数 + 命中率），用于判断前台缓存效果、是否需额外加速
- 文档与测试同步

app/Blog/Support/PageCacheMiddleware.php

@@ -28,12 +28,16 @@ class PageCacheMiddleware
         $ttl = (int) config('blog.page_cache_ttl', 300);
 
         if ($cached = Cache::get($key)) {
+            self::increment('hits');
+
             return response($cached['body'], 200, [
                 'Content-Type' => $cached['type'],
                 'Cache-Control' => 'public, max-age='.$ttl,
             ]);
         }
 
+        self::increment('misses');
+
         $response = $next($request);
 
         if ($response->getStatusCode() === 200) {
@@ -61,6 +65,35 @@ class PageCacheMiddleware
         return count((array) Cache::get(self::TAG.'_keys', []));
     }
 
+    /**
+     * 命中/未命中统计（按日滚动），用于判断前台缓存效果。
+     */
+    public static function stats(): array
+    {
+        $hits = (int) Cache::get(self::TAG.'_hits', 0);
+        $misses = (int) Cache::get(self::TAG.'_misses', 0);
+        $total = $hits + $misses;
+
+        return [
+            'hits' => $hits,
+            'misses' => $misses,
+            'count' => self::count(),
+            'rate' => $total > 0 ? round($hits / $total * 100, 1) : 0.0,
+        ];
+    }
+
+    public static function resetStats(): void
+    {
+        Cache::forget(self::TAG.'_hits');
+        Cache::forget(self::TAG.'_misses');
+    }
+
+    private static function increment(string $metric): void
+    {
+        $key = self::TAG.'_'.$metric;
+        Cache::put($key, (int) Cache::get($key, 0) + 1, now()->addDay());
+    }
+
     private static function rememberKey(string $key): void
     {
         $keys = (array) Cache::get(self::TAG.'_keys', []);

app/Blog/Support/PluginManager.php

@@ -81,6 +81,7 @@ class PluginManager
                 'title' => $manifest['title'] ?? $name,
                 'version' => $manifest['version'] ?? '0.0.0',
                 'description' => $manifest['description'] ?? '',
+                'usage' => $manifest['usage'] ?? '',
                 'author' => $manifest['author'] ?? '',
                 'enabled' => $this->isEnabled($basename),
                 'requires' => $requires,

app/Filament/Widgets/BlogStats.php

@@ -17,6 +17,8 @@ class BlogStats extends BaseWidget
 
     protected function getStats(): array
     {
+        $cache = \App\Blog\Support\PageCacheMiddleware::stats();
+
         return [
             Stat::make('文章', Post::published()->count())
                 ->description('总浏览量 '.number_format((float) Post::sum('views')))
@@ -26,6 +28,9 @@ class BlogStats extends BaseWidget
                 ->icon('heroicon-o-chat-bubble-left-right'),
             Stat::make('用户', User::count())
                 ->icon('heroicon-o-users'),
+            Stat::make('页面缓存', $cache['count'].' 条')
+                ->description('命中率 '.$cache['rate'].'%（命中 '.$cache['hits'].' / 未命中 '.$cache['misses'].'，按日滚动）')
+                ->icon('heroicon-o-bolt'),
         ];
     }
 }