feat: 外观支持自定义 CSS/JS，并升级发帖工作台与积分存量看板

后台可注入全站 CSS/JS（SSR 生效，CSS 可热换）；发帖/编辑改为锁一屏工作室；经济看板增加存量健康度；主题令牌与弹层误关一并收紧。

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

backend/service/setting.go

@@ -49,6 +49,10 @@ const (
 	SettingKeyAttachmentMaxCount = "attachment_max_count"
 	// SettingKeyImageMaxMB 正文插图上限（MB）；缺行=5
 	SettingKeyImageMaxMB = "image_max_mb"
+	// SettingKeyCustomCSS 全站自定义 CSS（外观页注入，空=无）
+	SettingKeyCustomCSS = "custom_css"
+	// SettingKeyCustomJS 全站自定义 JS（外观页注入，空=无）
+	SettingKeyCustomJS = "custom_js"
 )
 
 const (
@@ -70,6 +74,9 @@ const (
 	MinAttachmentMaxCount     = 1
 	MaxAttachmentMaxCount     = 20
 	MaxAttachmentExtCount     = 80
+
+	MaxCustomCSSRunes = 48000
+	MaxCustomJSRunes  = 48000
 )
 
 // DefaultAttachmentExts 论坛向默认允许扩展名（含安装包/脚本/网页）
@@ -115,6 +122,8 @@ type PublicSiteSettings struct {
 	AttachmentMaxMB      int      `json:"attachment_max_mb"`
 	AttachmentMaxCount   int      `json:"attachment_max_count"`
 	ImageMaxMB           int      `json:"image_max_mb"`
+	CustomCSS            string   `json:"custom_css"`
+	CustomJS             string   `json:"custom_js"`
 }
 
 // SettingService 站点级键值设置
@@ -316,6 +325,18 @@ func (s *SettingService) Public() (PublicSiteSettings, error) {
 		return out, err
 	}
 	out.ImageMaxMB = imgMB
+
+	css, err := s.CustomCSS()
+	if err != nil {
+		return out, err
+	}
+	out.CustomCSS = css
+
+	js, err := s.CustomJS()
+	if err != nil {
+		return out, err
+	}
+	out.CustomJS = js
 	return out, nil
 }
 
@@ -767,3 +788,65 @@ func (s *SettingService) ImageMaxBytes() (int64, error) {
 	}
 	return int64(mb) << 20, nil
 }
+
+func sanitizeCustomSnippet(s, closer string, maxRunes int) (string, error) {
+	s = strings.TrimSpace(s)
+	if strings.ContainsRune(s, 0) {
+		return "", ErrInvalidSiteSetting
+	}
+	if utf8.RuneCountInString(s) > maxRunes {
+		return "", ErrInvalidSiteSetting
+	}
+	if closer != "" && strings.Contains(strings.ToLower(s), closer) {
+		return "", ErrInvalidSiteSetting
+	}
+	return s, nil
+}
+
+// CustomCSS 全站自定义 CSS。缺行/空=无。
+func (s *SettingService) CustomCSS() (string, error) {
+	v, found, err := s.getValue(SettingKeyCustomCSS)
+	if err != nil || !found {
+		return "", err
+	}
+	out, nerr := sanitizeCustomSnippet(v, "</style", MaxCustomCSSRunes)
+	if nerr != nil {
+		return "", nil
+	}
+	return out, nil
+}
+
+func (s *SettingService) SetCustomCSS(css string) error {
+	normalized, err := sanitizeCustomSnippet(css, "</style", MaxCustomCSSRunes)
+	if err != nil {
+		return err
+	}
+	if normalized == "" {
+		return s.deleteKey(SettingKeyCustomCSS)
+	}
+	return s.putValue(SettingKeyCustomCSS, normalized)
+}
+
+// CustomJS 全站自定义 JS。缺行/空=无。
+func (s *SettingService) CustomJS() (string, error) {
+	v, found, err := s.getValue(SettingKeyCustomJS)
+	if err != nil || !found {
+		return "", err
+	}
+	out, nerr := sanitizeCustomSnippet(v, "</script", MaxCustomJSRunes)
+	if nerr != nil {
+		return "", nil
+	}
+	return out, nil
+}
+
+func (s *SettingService) SetCustomJS(js string) error {
+	normalized, err := sanitizeCustomSnippet(js, "</script", MaxCustomJSRunes)
+	if err != nil {
+		return err
+	}
+	if normalized == "" {
+		return s.deleteKey(SettingKeyCustomJS)
+	}
+	return s.putValue(SettingKeyCustomJS, normalized)
+}