feat(kol): cache marketplace and generation reads with singleflight

Add cache-aside + singleflight to KOL marketplace list/detail, my-subscription
prompts, and generation schema lookups. Invalidate the shared public-facing
caches when subscriptions are added/revoked (ops) or KOL profile is updated.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/transport/kol_manage_handler.go

@@ -36,7 +36,7 @@ type kolAssistStreamEvent struct {
 }
 
 func NewKolManageHandler(a *bootstrap.App, assets *AssetHandler) *KolManageHandler {
-	profileSvc := app.NewKolProfileService(a.KolProfiles).WithObjectStorage(a.ObjectStorage)
+	profileSvc := app.NewKolProfileService(a.KolProfiles).WithObjectStorage(a.ObjectStorage).WithCache(a.Cache)
 
 	return &KolManageHandler{
 		profileSvc: profileSvc,

server/internal/tenant/transport/kol_marketplace_handler.go

@@ -18,7 +18,7 @@ type KolMarketplaceHandler struct {
 
 func NewKolMarketplaceHandler(a *bootstrap.App) *KolMarketplaceHandler {
 	return &KolMarketplaceHandler{
-		svc: app.NewKolMarketplaceService(a.KolMarketplace, a.KolSubscriptions),
+		svc: app.NewKolMarketplaceService(a.KolMarketplace, a.KolSubscriptions).WithCache(a.Cache),
 		genSvc: app.NewKolGenerationService(
 			a.DB,
 			a.KolSubscriptions,