refactor(zone): remove legacy route domain storage

第二阶段清理：删除 of_managed_domains 与 of_proxy_routes 冗余域名/证书列，
移除 ManagedDomain 模型与 API、路由侧 legacy 字段维护，以及前端 WebsiteService。
ImportLegacy 在旧列/旧表缺失时跳过对应源，保持幂等。

internal/model/openflare_proxy_route.go

@@ -11,22 +11,16 @@ import (
 )
 
 // ProxyRoute OpenFlare 代理规则实体。
+// 域名与证书仅通过 of_zone_domains 关联，不再持久化在本表。
 type ProxyRoute struct {
-	ID       uint   `json:"id" gorm:"primaryKey;autoIncrement"`
-	SiteName string `json:"site_name" gorm:"size:255;not null;default:''"`
-	// Legacy mirrors are maintained from ZoneDomain bindings until the staged
-	// schema cleanup. They are not route API fields.
-	Domain               string       `json:"-" gorm:"uniqueIndex;size:255;not null"`
-	Domains              string       `json:"-" gorm:"type:text;not null;default:'[]'"`
+	ID                   uint         `json:"id" gorm:"primaryKey;autoIncrement"`
+	SiteName             string       `json:"site_name" gorm:"size:255;not null;default:''"`
 	OriginID             *uint        `json:"origin_id" gorm:"index"`
 	OriginURL            string       `json:"origin_url" gorm:"size:2048;not null"`
 	OriginHost           string       `json:"origin_host" gorm:"size:255"`
 	Upstreams            string       `json:"upstreams" gorm:"type:text;not null;default:'[]'"`
 	Enabled              bool         `json:"enabled" gorm:"not null;default:true"`
 	EnableHTTPS          bool         `json:"enable_https" gorm:"column:enable_https;not null;default:false"`
-	CertID               *uint        `json:"-"`
-	CertIDs              string       `json:"-" gorm:"type:text;not null;default:'[]'"`
-	DomainCertIDs        string       `json:"-" gorm:"type:text;not null;default:'[]'"`
 	RedirectHTTP         bool         `json:"redirect_http" gorm:"not null;default:false"`
 	LimitConnPerServer   int          `json:"limit_conn_per_server" gorm:"not null;default:0"`
 	LimitConnPerIP       int          `json:"limit_conn_per_ip" gorm:"not null;default:0"`
@@ -81,17 +75,12 @@ func CreateProxyRouteRecord(ctx context.Context, route *ProxyRoute) error {
 func UpdateProxyRouteRecord(ctx context.Context, route *ProxyRoute) error {
 	return db.DB(ctx).Model(&ProxyRoute{}).Where("id = ?", route.ID).Updates(map[string]any{
 		"site_name":              route.SiteName,
-		"domain":                 route.Domain,
-		"domains":                route.Domains,
 		"origin_id":              route.OriginID,
 		"origin_url":             route.OriginURL,
 		"origin_host":            route.OriginHost,
 		"upstreams":              route.Upstreams,
 		colEnabled:               route.Enabled,
 		"enable_https":           route.EnableHTTPS,
-		"cert_id":                route.CertID,
-		"cert_ids":               route.CertIDs,
-		"domain_cert_ids":        route.DomainCertIDs,
 		"redirect_http":          route.RedirectHTTP,
 		"limit_conn_per_server":  route.LimitConnPerServer,
 		"limit_conn_per_ip":      route.LimitConnPerIP,