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/home/service.go

@@ -31,6 +31,7 @@ type Service struct {
 	Repo     *repository.HomeToolsRepo
 	Tips     *repository.HomeDailyTipsRepo
 	Profiles *repository.ProfileRepo
+	CMS      *repository.AdminRepo
 	LLM      *deepseek.Client
 }
 
@@ -39,6 +40,24 @@ func (s *Service) ListPublic(ctx context.Context) ([]repository.HomeTool, error)
 	return s.Repo.ListEnabled(ctx)
 }
 
+// ListPublicBanners returns active banners for placement (default home).
+func (s *Service) ListPublicBanners(ctx context.Context, placement string) ([]repository.BannerRow, error) {
+	if placement == "" {
+		placement = "home"
+	}
+	if s.CMS == nil {
+		return []repository.BannerRow{}, nil
+	}
+	items, err := s.CMS.ListActiveBanners(ctx, placement)
+	if err != nil {
+		return nil, err
+	}
+	if items == nil {
+		items = []repository.BannerRow{}
+	}
+	return items, nil
+}
+
 // ListAdmin returns all tools.
 func (s *Service) ListAdmin(ctx context.Context) ([]repository.HomeTool, error) {
 	return s.Repo.ListAll(ctx)