feat: 首页增加内存缓存（30s TTL）

- 新增 internal/cache/home_cache.go，实现带 TTL 的首页文章列表内存缓存
- frontend.go 首页 handler 优先读取缓存，未命中/过期时查询 DB 并回填
- PostService 注入失效回调，在 Create/Update/Delete/Approve 后自动失效缓存
- 减少首页每次请求都查 DB 的开销

internal/router/deps_core.go

@@ -4,6 +4,7 @@ import (
 	"log"
 	"time"
 
+	"metazone.cc/metalab/internal/cache"
 	"metazone.cc/metalab/internal/config"
 	"metazone.cc/metalab/internal/controller"
 	adminCtrl "metazone.cc/metalab/internal/controller/admin"
@@ -42,6 +43,7 @@ type dependencies struct {
 	favoriteCtrl    *controller.FavoriteController
 	favoriteService *service.FavoriteService
 	trendsService   *service.TrendsService
+	homeCache       *cache.HomePageCache
 }
 
 func buildDepsCore(db *gorm.DB, cfg *config.Config, siteSettings *config.SiteSettings, redisClient *redis.Client) (

internal/router/deps_extra.go

@@ -1,6 +1,9 @@
 package router
 
 import (
+	"time"
+
+	"metazone.cc/metalab/internal/cache"
 	"metazone.cc/metalab/internal/config"
 	"metazone.cc/metalab/internal/controller"
 	adminCtrl "metazone.cc/metalab/internal/controller/admin"
@@ -99,6 +102,10 @@ func buildDeps(db *gorm.DB, cfg *config.Config, siteSettings *config.SiteSetting
 
 	maintenanceMdw := middleware.NewMaintenanceMiddleware(cfg, siteSettings, sessionMgr)
 
+	// 首页内存缓存（30s TTL），文章变更时失效
+	homeCache := cache.NewHomePageCache(30 * time.Second)
+	postService.WithHomePageInvalidator(func() { homeCache.Invalidate() })
+
 	return &dependencies{
 		authCtrl: authCtrl, authMdw: authMdw, maintenanceMdw: maintenanceMdw,
 		settingsCtrl: settingsCtrl,
@@ -119,5 +126,6 @@ func buildDeps(db *gorm.DB, cfg *config.Config, siteSettings *config.SiteSetting
 		favoriteCtrl:    favoriteCtrl,
 		favoriteService: favoriteService,
 		trendsService:   trendsService,
+		homeCache:       homeCache,
 	}
 }

internal/router/frontend.go

@@ -22,10 +22,16 @@ func setupFrontendRoutes(r *gin.Engine, cfg *config.Config, d *dependencies) {
 	})
 	{
 		pages.GET("/", func(c *gin.Context) {
-			posts, total, err := d.postService.List("", 1, 6)
-			if err != nil {
-				posts = nil
-				total = 0
+			posts, total, ok := d.homeCache.Get()
+			if !ok {
+				var err error
+				posts, total, err = d.postService.List("", 1, 6)
+				if err != nil {
+					posts = nil
+					total = 0
+				} else {
+					d.homeCache.Set(posts, total)
+				}
 			}
 			c.HTML(http.StatusOK, "home/index.html", common.BuildPageData(c, gin.H{
 				"Title":     "首页",