feat(cache): add read-through cache layer across all app services

Introduce a generic read-through caching infrastructure and wire it into
all major tenant app services to reduce database load on hot read paths.

Key changes:
- Add `DeletePrefix` to Cache interface with memory (prefix scan) and
  Redis (SCAN + DEL) implementations
- New `readthrough.go`: generic `LoadJSON` / `LoadJSONWithEmpty` helpers
  backed by singleflight to prevent cache stampedes; supports jittered TTL
- New `cache_support.go`: centralized cache key builders and invalidation
  helpers for all entities (workspace, brand, prompt rules, schedule tasks,
  articles)
- Wire optional cache into ArticleService, BrandService, WorkspaceService,
  PromptRuleService, ScheduleTaskService, TemplateService, MediaService,
  PromptGenerateService via `WithCache()` builder pattern
- ScheduleDispatchWorker invalidates schedule task cache after dispatching
- ArticleService gains a new `Detail` endpoint with empty-result caching
- Update cmd entrypoints and transport handlers to propagate cache

server/internal/tenant/repository/article_repo.go

@@ -4,6 +4,7 @@ import (
 	"context"
 
 	"github.com/geo-platform/tenant-api/internal/tenant/repository/generated"
+	"github.com/jackc/pgx/v5"
 )
 
 type CreateArticleInput struct {
@@ -86,17 +87,37 @@ func (r *articleRepository) CreateArticleVersion(ctx context.Context, input Crea
 }
 
 func (r *articleRepository) UpdateArticleCurrentVersion(ctx context.Context, articleID, tenantID, versionID int64) error {
-	return r.q.UpdateArticleCurrentVersion(ctx, generated.UpdateArticleCurrentVersionParams{
-		VersionID: pgInt8(&versionID),
-		ID:        articleID,
-		TenantID:  tenantID,
-	})
+	tag, err := r.db.Exec(ctx, `
+		UPDATE articles
+		SET current_version_id = $1,
+		    updated_at = NOW()
+		WHERE id = $2
+		  AND tenant_id = $3
+		  AND deleted_at IS NULL
+	`, pgInt8(&versionID), articleID, tenantID)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return pgx.ErrNoRows
+	}
+	return nil
 }
 
 func (r *articleRepository) UpdateArticleGenerateStatus(ctx context.Context, articleID, tenantID int64, status string) error {
-	return r.q.UpdateArticleGenerateStatus(ctx, generated.UpdateArticleGenerateStatusParams{
-		Status:   status,
-		ID:       articleID,
-		TenantID: tenantID,
-	})
+	tag, err := r.db.Exec(ctx, `
+		UPDATE articles
+		SET generate_status = $1,
+		    updated_at = NOW()
+		WHERE id = $2
+		  AND tenant_id = $3
+		  AND deleted_at IS NULL
+	`, status, articleID, tenantID)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return pgx.ErrNoRows
+	}
+	return nil
 }