feat(ECR-041): OpsCMS Banner 薄写面（Write-Wave 首刀）

Admin POST/PUT + admin.cms.write/审计；C 端 GET /home/banners；首页投影回退静态 homeFeeds；migration 000051；不碰 FeedSlot/支付/UGC。

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

apps/api/internal/service/admin/rbac.go

@@ -31,6 +31,7 @@ const (
 	PermAIConfigRead         = "admin.ai_config.read"
 	PermCrisisRead           = "admin.crisis.read"
 	PermCMSRead              = "admin.cms.read"
+	PermCMSWrite             = "admin.cms.write"
 	PermPrivacyRead = "admin.privacy.read"
 	PermExploreRead = "admin.explore.read"
 	PermGrowthRead = "admin.growth.read"
@@ -43,7 +44,7 @@ var knownPermissions = map[string]struct{}{
 	PermUsersStatusWrite: {}, PermMembershipPlansRead: {}, PermMembershipPlansWrite: {},
 	PermMembershipCodesRead: {}, PermMembershipCodesWrite: {},
 	PermAskRead: {}, PermAskTranscriptRead: {}, PermAskFeedbackWrite: {}, PermContentSafetyRead: {},
-	PermAIConfigRead: {}, PermCrisisRead: {}, PermCMSRead: {}, PermGrowthRead: {}, PermExploreRead: {}, PermPrivacyRead: {},
+	PermAIConfigRead: {}, PermCrisisRead: {}, PermCMSRead: {}, PermCMSWrite: {}, PermGrowthRead: {}, PermExploreRead: {}, PermPrivacyRead: {},
 }
 
 var (