feat: 对接稿件审核通知系统 + 消息页面系统消息区域

- 新增通知类型 post_approved / post_rejected
- PostService.Approve/Reject 完成后通知作者（通知失败不影响主流程）
- NotificationService 新增 NotifyPostApproved/NotifyPostRejected 方法
- 消息页面顶部增加系统消息标识和分隔线，之下为全部消息列表
- 稿件审核通过通知卡片点击跳转到 /posts/{id} 页面
- 稿件审核拒绝通知卡片点击跳转到 /studio/posts 创作中心
- 新增 postNotifier 接口遵循 ISP 原则

internal/service/notification_service.go

@@ -110,3 +110,20 @@ func (s *NotificationService) NotifyAuditRejected(userID uint, auditType, reason
 		content,
 		&relatedID)
 }
+
+// NotifyPostApproved 稿件审核通过通知
+func (s *NotificationService) NotifyPostApproved(userID uint, postTitle string, postID uint) {
+	title := "稿件审核通过"
+	content := "你的稿件《" + postTitle + "》已通过审核，现已公开发布"
+	_ = s.Create(userID, model.NotifyPostApproved, title, content, &postID)
+}
+
+// NotifyPostRejected 稿件审核拒绝通知
+func (s *NotificationService) NotifyPostRejected(userID uint, postTitle, reason string, postID uint) {
+	title := "稿件审核未通过"
+	content := "你的稿件《" + postTitle + "》未通过审核"
+	if reason != "" {
+		content += "，理由：" + reason
+	}
+	_ = s.Create(userID, model.NotifyPostRejected, title, content, &postID)
+}

internal/service/post_service.go

@@ -75,15 +75,17 @@ func generateExcerpt(md string) string {
 
 // PostService 帖子业务逻辑
 type PostService struct {
-	repo postStore
-	ss   *config.SiteSettings
+	repo     postStore
+	ss       *config.SiteSettings
+	notifier postNotifier
 }
 
 // NewPostService 构造函数
-func NewPostService(repo postStore, ss *config.SiteSettings) *PostService {
+func NewPostService(repo postStore, ss *config.SiteSettings, notifier postNotifier) *PostService {
 	return &PostService{
-		repo: repo,
-		ss:   ss,
+		repo:     repo,
+		ss:       ss,
+		notifier: notifier,
 	}
 }
 
@@ -263,8 +265,10 @@ func (s *PostService) Approve(postID uint) error {
 		return err
 	}
 
+	wasRevision := post.PendingBody != ""
+
 	// 修订审核：将待审内容覆盖到正式字段
-	if post.PendingBody != "" {
+	if wasRevision {
 		post.Title = post.PendingTitle
 		post.Body = post.PendingBody
 		post.Excerpt = generateExcerpt(post.PendingBody)
@@ -272,7 +276,14 @@ func (s *PostService) Approve(postID uint) error {
 		post.PendingBody = ""
 		post.Status = model.PostStatusApproved
 		post.RejectReason = ""
-		return s.repo.Update(post)
+		if err := s.repo.Update(post); err != nil {
+			return err
+		}
+		// 通知作者修订审核通过
+		if s.notifier != nil {
+			s.notifier.NotifyPostApproved(post.UserID, post.Title, post.ID)
+		}
+		return nil
 	}
 
 	// 首次审核通过
@@ -281,7 +292,14 @@ func (s *PostService) Approve(postID uint) error {
 	}
 	post.Status = model.PostStatusApproved
 	post.RejectReason = ""
-	return s.repo.Update(post)
+	if err := s.repo.Update(post); err != nil {
+		return err
+	}
+	// 通知作者审核通过
+	if s.notifier != nil {
+		s.notifier.NotifyPostApproved(post.UserID, post.Title, post.ID)
+	}
+	return nil
 }
 
 // Reject 退回：pending/approved → rejected；修订退回则清空 Pending 保持 approved
@@ -299,13 +317,27 @@ func (s *PostService) Reject(postID uint, reason string) error {
 		post.PendingTitle = ""
 		post.PendingBody = ""
 		post.RejectReason = reason
-		return s.repo.Update(post)
+		if err := s.repo.Update(post); err != nil {
+			return err
+		}
+		// 通知作者修订被退回
+		if s.notifier != nil {
+			s.notifier.NotifyPostRejected(post.UserID, post.Title, reason, post.ID)
+		}
+		return nil
 	}
 
 	// 普通退回（首次审核）
 	post.Status = model.PostStatusRejected
 	post.RejectReason = reason
-	return s.repo.Update(post)
+	if err := s.repo.Update(post); err != nil {
+		return err
+	}
+	// 通知作者审核被退回
+	if s.notifier != nil {
+		s.notifier.NotifyPostRejected(post.UserID, post.Title, reason, post.ID)
+	}
+	return nil
 }
 
 // Lock 锁定：设置 IsLocked 标志，禁止编辑，不改变帖子发布状态

internal/service/repository.go

@@ -53,4 +53,10 @@ type spaceUserStore interface {
 // spacePostStore SpaceService 所需的最小帖子仓储接口（ISP：1 个方法）
 type spacePostStore interface {
 	FindByUserID(userID uint, offset, limit int) ([]model.Post, int64, error)
+}
+
+// postNotifier PostService 所需的通知服务接口（ISP：2 个方法）
+type postNotifier interface {
+	NotifyPostApproved(userID uint, postTitle string, postID uint)
+	NotifyPostRejected(userID uint, postTitle, reason string, postID uint)
 }