feat: 注册准则阅读控制 + Footer 合规信息

准则阅读（三层控制）：
- registration.show_guidelines — 弹窗/复选框模式
- registration.force_guidelines — 是否强制倒计时+滚动
- registration.guidelines_timer — 倒计时秒数

Footer 合规（8 字段，空值不显示，链接纯手写）：
- site.operator_name / site.icp_number / site.icp_license
- site.police_number / site.wenwangwen / site.algorithm_filing
- site.privacy_url / site.terms_url
- 新增 safeHTML 模板函数输出不转义 HTML

internal/middleware/site_info.go

@@ -16,7 +16,16 @@ func InjectSiteInfo(siteSettings *config.SiteSettings) gin.HandlerFunc {
 		c.Set("site_contact_email", info.ContactEmail)
 		c.Set("site_framework", info.Framework)
 		c.Set("site_copyright_start", info.CopyrightStart)
+		c.Set("site_operator_name", info.OperatorName)
+		c.Set("site_icp_number", info.ICPNumber)
+		c.Set("site_icp_license", info.ICPLicense)
+		c.Set("site_police_number", info.PoliceNumber)
+		c.Set("site_wenwangwen", info.WenWangWen)
+		c.Set("site_algorithm_filing", info.AlgorithmFiling)
+		c.Set("site_privacy_url", info.PrivacyURL)
+		c.Set("site_terms_url", info.TermsURL)
 		c.Set("is_maintenance", siteSettings.IsMaintenanceEnabled())
+		c.Set("registration_guidelines_timer", siteSettings.GuidelinesTimer())
 		c.Next()
 	}
 }