feat(tenant): inject brand description context into every generation path

Include the current brand description in template, custom, imitation,
and KOL article-generation prompts while bounding prompt growth.

- Add a shared brand-context builder that resolves the current brand,
  compacts long descriptions, and caps rendered output at 2000 runes.
- Snapshot a structured brand prompt context on queued tasks so old
  jobs stay reproducible and retries stay stable.
- Route brand-profile facts through the existing typed fact guard so
  founding dates and year counts get the same pre-persistence validation
  as RAG facts, with brand facts outranking conflicting RAG facts.
- Fix the KOL creator to attach the brand scope its worker consumes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/internal/tenant/app/kol_generation_service.go

@@ -255,6 +255,10 @@ func (s *KolGenerationService) enqueue(ctx context.Context, input kolGenerationE
 	if row.PublishedRevisionNo != nil && *row.PublishedRevisionNo > 0 {
 		promptRevisionNo = *row.PublishedRevisionNo
 	}
+	brandPromptContext, err := loadBrandPromptContext(ctx, s.pool, actor.TenantID, input.BrandID)
+	if err != nil {
+		return nil, err
+	}
 
 	balance, err := s.quotaRepo.GetCurrentBalance(ctx, actor.TenantID, "article_generation")
 	if err != nil || balance < 1 {
@@ -271,12 +275,13 @@ func (s *KolGenerationService) enqueue(ctx context.Context, input kolGenerationE
 		"prompt_revision_no":     promptRevisionNo,
 		"variables":              variables,
 		"enable_web_search":      enableWebSearch,
-		"knowledge_group_ids":    knowledgeGroupIDs,
 		"schema_snapshot":        json.RawMessage(prompt.SchemaJSON),
 		"card_config_snapshot":   json.RawMessage(prompt.CardConfigJSON),
 		"rendered_prompt_hash":   renderedPromptHash,
 		"rendered_prompt":        renderedPrompt,
 	}
+	attachKolGenerationKnowledgeScope(taskInput, input.BrandID, knowledgeGroupIDs)
+	taskInput = attachBrandPromptContext(taskInput, brandPromptContext)
 	if input.Schedule != nil {
 		attachKolScheduleTaskInput(taskInput, *input.Schedule)
 	}
@@ -446,6 +451,14 @@ func (s *KolGenerationService) enqueue(ctx context.Context, input kolGenerationE
 	}, nil
 }
 
+func attachKolGenerationKnowledgeScope(input map[string]any, brandID int64, knowledgeGroupIDs []int64) {
+	if input == nil {
+		return
+	}
+	input["brand_id"] = brandID
+	input["knowledge_group_ids"] = normalizeInt64IDs(knowledgeGroupIDs)
+}
+
 func attachKolScheduleTaskInput(input map[string]any, schedule ScheduleKolGenerationInput) {
 	input["generation_mode"] = "schedule"
 	input["schedule_task_id"] = schedule.ScheduleTaskID