feat: 文章锁定/解锁时触发系统通知

- 新增 NotifyPostLocked/NotifyPostUnlocked 通知类型
- Lock/Unlock 方法执行后通过 notifier 发送通知给作者
- 锁定时通知含锁定理由，解锁时通知已解除锁定
- 新增类型归入稿件审核分类和 system tab

internal/model/notification.go

@@ -6,6 +6,8 @@ const (
 	NotifyAuditRejected   = "audit_rejected"
 	NotifyPostApproved    = "post_approved"
 	NotifyPostRejected    = "post_rejected"
+	NotifyPostLocked      = "post_locked"
+	NotifyPostUnlocked    = "post_unlocked"
 	NotifyLevelUp         = "level_up"
 	NotifyComment         = "comment"
 	NotifyCommentReply    = "comment_reply"
@@ -32,6 +34,8 @@ var NotifyTypeNames = map[string]string{
 	NotifyAuditRejected:  "资料审核",
 	NotifyPostApproved:   "稿件审核",
 	NotifyPostRejected:   "稿件审核",
+	NotifyPostLocked:     "稿件审核",
+	NotifyPostUnlocked:   "稿件审核",
 	NotifyLevelUp:        "等级提升",
 	NotifyComment:        "评论",
 	NotifyCommentReply:   "回复",
@@ -45,6 +49,8 @@ var NotifyCategory = map[string]string{
 	NotifyAuditRejected:  "system",
 	NotifyPostApproved:   "system",
 	NotifyPostRejected:   "system",
+	NotifyPostLocked:     "system",
+	NotifyPostUnlocked:   "system",
 	NotifyLevelUp:        "system",
 	NotifyComment:        "mention",
 	NotifyCommentReply:   "mention",