feat: 后台增加开放消息开关

关闭后前台隐藏私聊/群聊入口并由后端拦截；同步去掉公告页重复计数胶囊。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/handler/setting.go

@@ -27,6 +27,7 @@ type updateSettingsRequest struct {
 	SiteDescription      *string `json:"site_description"`
 	AllowRegister        *bool   `json:"allow_register"`
 	AllowComments        *bool   `json:"allow_comments"`
+	AllowMessages        *bool   `json:"allow_messages"`
 	PostCooldownHours    *int    `json:"post_cooldown_hours"`
 	CodeBlockAutoFold    *bool   `json:"code_block_auto_fold"`
 	CodeBlockFoldLines   *int    `json:"code_block_fold_lines"`
@@ -45,6 +46,7 @@ func settingsPayload(saved service.PublicSiteSettings) gin.H {
 		"site_description":       saved.SiteDescription,
 		"allow_register":         saved.AllowRegister,
 		"allow_comments":         saved.AllowComments,
+		"allow_messages":         saved.AllowMessages,
 		"post_cooldown_hours":    saved.PostCooldownHours,
 		"code_block_auto_fold":   saved.CodeBlockAutoFold,
 		"code_block_fold_lines":  saved.CodeBlockFoldLines,
@@ -65,6 +67,7 @@ func (h *Handlers) UpdateSettings(c *gin.Context) {
 	}
 	if req.Accent == nil && req.TrustReviewedPublish == nil && req.SiteName == nil &&
 		req.SiteDescription == nil && req.AllowRegister == nil && req.AllowComments == nil &&
+		req.AllowMessages == nil &&
 		req.PostCooldownHours == nil && req.CodeBlockAutoFold == nil && req.CodeBlockFoldLines == nil &&
 		req.UIAnimations == nil && req.AnimCodeFold == nil && req.AnimSmoothScroll == nil &&
 		req.AnimChrome == nil && req.PostLinkNewTab == nil {
@@ -120,6 +123,12 @@ func (h *Handlers) UpdateSettings(c *gin.Context) {
 			return
 		}
 	}
+	if req.AllowMessages != nil {
+		if err := h.Setting.SetAllowMessages(*req.AllowMessages); err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": "保存站点设置失败"})
+			return
+		}
+	}
 	if req.PostCooldownHours != nil {
 		if err := h.Setting.SetPostCooldownHours(*req.PostCooldownHours); err != nil {
 			if errors.Is(err, service.ErrInvalidSiteSetting) {