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/common/helper.go

@@ -175,5 +175,32 @@ func injectSiteInfo(c *gin.Context, data gin.H) {
 	if copyrightStart, exists := c.Get("site_copyright_start"); exists {
 		data["CopyrightStart"] = copyrightStart
 	}
+	if operatorName, exists := c.Get("site_operator_name"); exists {
+		data["OperatorName"] = operatorName
+	}
+	if icpNumber, exists := c.Get("site_icp_number"); exists {
+		data["ICPNumber"] = icpNumber
+	}
+	if icpLicense, exists := c.Get("site_icp_license"); exists {
+		data["ICPLicense"] = icpLicense
+	}
+	if policeNumber, exists := c.Get("site_police_number"); exists {
+		data["PoliceNumber"] = policeNumber
+	}
+	if wenwangwen, exists := c.Get("site_wenwangwen"); exists {
+		data["WenWangWen"] = wenwangwen
+	}
+	if algorithmFiling, exists := c.Get("site_algorithm_filing"); exists {
+		data["AlgorithmFiling"] = algorithmFiling
+	}
+	if privacyURL, exists := c.Get("site_privacy_url"); exists {
+		data["PrivacyURL"] = privacyURL
+	}
+	if termsURL, exists := c.Get("site_terms_url"); exists {
+		data["TermsURL"] = termsURL
+	}
+	if guidelinesTimer, exists := c.Get("registration_guidelines_timer"); exists {
+		data["GuidelinesTimer"] = guidelinesTimer
+	}
 	data["CurrentYear"] = time.Now().Year()
 }