feat(admin): 独立后台壳、站点分析与聊天监管，公开站拆出主题切换与访问埋点

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

backend/service/setting.go

@@ -35,6 +35,8 @@ const (
 	SettingKeyAnimSmoothScroll = "anim_smooth_scroll"
 	// SettingKeyAnimChrome 装饰入场（列表/Toast/点赞等）；缺行视为开启
 	SettingKeyAnimChrome = "anim_chrome"
+	// SettingKeyPostLinkNewTab 帖子/评论 Markdown 外链是否新标签打开；缺行视为开启（聊天链接始终新开，不受此键控制）
+	SettingKeyPostLinkNewTab = "post_link_new_tab"
 )
 
 const (
@@ -72,6 +74,7 @@ type PublicSiteSettings struct {
 	AnimCodeFold          bool   `json:"anim_code_fold"`
 	AnimSmoothScroll      bool   `json:"anim_smooth_scroll"`
 	AnimChrome            bool   `json:"anim_chrome"`
+	PostLinkNewTab        bool   `json:"post_link_new_tab"`
 }
 
 // SettingService 站点级键值设置
@@ -139,6 +142,7 @@ func (s *SettingService) Public() (PublicSiteSettings, error) {
 		AnimCodeFold:         true,
 		AnimSmoothScroll:     true,
 		AnimChrome:           true,
+		PostLinkNewTab:       true,
 	}
 	accent, err := s.AccentColor()
 	if err != nil {
@@ -224,6 +228,12 @@ func (s *SettingService) Public() (PublicSiteSettings, error) {
 		return out, err
 	}
 	out.AnimChrome = animChrome
+
+	linkNewTab, err := s.PostLinkNewTab()
+	if err != nil {
+		return out, err
+	}
+	out.PostLinkNewTab = linkNewTab
 	return out, nil
 }
 
@@ -433,3 +443,16 @@ func (s *SettingService) AnimChrome() (bool, error) {
 func (s *SettingService) SetAnimChrome(on bool) error {
 	return s.setBoolDefaultTrue(SettingKeyAnimChrome, on)
 }
+
+// PostLinkNewTab 帖子/评论 Markdown 外链是否新标签打开。缺行视为开启。
+func (s *SettingService) PostLinkNewTab() (bool, error) {
+	v, found, err := s.getValue(SettingKeyPostLinkNewTab)
+	if err != nil {
+		return true, err
+	}
+	return parseBoolDefaultTrue(v, found), nil
+}
+
+func (s *SettingService) SetPostLinkNewTab(on bool) error {
+	return s.setBoolDefaultTrue(SettingKeyPostLinkNewTab, on)
+}