feat(kol): enrich assist generate with URL references and template prompt

- Add kolAssistURLResolver that fetches reference articles via the Ark
  URL extractor when the user's description contains http(s) links, and
  merges up to kolAssistReferenceContentMaxRunes of extracted content
  into the generate description.
- Rewrite the generate user prompt into a strict template-authoring
  brief: output only the final prompt template in Chinese, parameterize
  variable info as {{placeholder}}, require at least 3 placeholders
  when references exist, and cover goal/topic/title/structure/style/
  interaction/constraints.
- Wire LLMConfig and logger through NewKolAssistService and the
  handler.

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

server/internal/tenant/transport/kol_manage_handler.go

@@ -42,7 +42,7 @@ func NewKolManageHandler(a *bootstrap.App, assets *AssetHandler) *KolManageHandl
 		profileSvc: profileSvc,
 		pkgSvc:     app.NewKolPackageService(profileSvc, a.KolPackages, a.KolPrompts).WithCache(a.Cache),
 		promptSvc:  app.NewKolPromptService(a.DB, profileSvc, a.KolPackages, a.KolPrompts, a.KolSubscriptions, a.KolPromptAsset).WithCache(a.Cache),
-		assistSvc:  app.NewKolAssistService(profileSvc, a.KolAssists, a.LLM, a.RabbitMQ),
+		assistSvc:  app.NewKolAssistService(profileSvc, a.KolAssists, a.LLM, a.RabbitMQ, a.Config.LLM, a.Logger),
 		assets:     assets,
 	}
 }