feat(admin-brand): add question expansion service and related functionality

- Implemented QuestionExpansionService for generating and materializing questions based on combinations and AI distillation.
- Added question metadata classification logic to infer intent and layer of questions.
- Created API handlers for question expansion operations including combination preview, AI distillation, metadata classification, and materialization.
- Introduced database migrations to support new question-related fields and constraints in brand_questions and brand_keywords tables.
- Added caching mechanism for AI distillation results to improve performance.
- Defined JSON schemas for question distillation responses to ensure data integrity.

server/internal/bootstrap/bootstrap.go

@@ -56,6 +56,7 @@ type App struct {
 	DesktopDispatch         *stream.DesktopDispatchHub
 	Cache                   cache.Cache
 	BrandService            *tenantapp.BrandService
+	QuestionExpansion       *tenantapp.QuestionExpansionService
 	MonitoringService       *tenantapp.MonitoringService
 	KolProfiles             repository.KolProfileRepository
 	KolPackages             repository.KolPackageRepository
@@ -145,6 +146,7 @@ func New(configPath string) (*App, error) {
 		DeleteScanCount:  cfg.Cache.DeleteScanCount,
 	})
 	brandService := tenantapp.NewBrandService(pool, monitoringPool, auditLogs, cfg.BrandLibrary).WithCache(appCache)
+	questionExpansion := tenantapp.NewQuestionExpansionService(pool, llmClient, brandService).WithCache(appCache)
 	monitoringService := tenantapp.NewMonitoringService(pool, monitoringPool, mqClient, cfg.MonitoringDispatch, cfg.BrandLibrary, logger).WithRedis(rdb)
 	kolProfiles := repository.NewKolProfileRepository(pool)
 	kolPackages := repository.NewKolPackageRepository(pool)
@@ -214,6 +216,7 @@ func New(configPath string) (*App, error) {
 		DesktopDispatch:         desktopDispatch,
 		Cache:                   appCache,
 		BrandService:            brandService,
+		QuestionExpansion:       questionExpansion,
 		MonitoringService:       monitoringService,
 		KolProfiles:             kolProfiles,
 		KolPackages:             kolPackages,