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.

packages/shared-types/src/index.ts

@@ -1214,6 +1214,7 @@ export interface Brand {
   status: string
   keyword_count: number
   question_count: number
+  competitor_count?: number
   created_at: string
   updated_at?: string
 }
@@ -1257,7 +1258,75 @@ export interface BrandLibrarySummary {
   max_keywords: number
   used_keywords: number
   remaining_keywords: number
+  max_questions: number
+  used_questions: number
+  remaining_questions: number
   max_questions_per_keyword: number
+  max_questions_per_brand: number
+}
+
+export type QuestionSource = 'manual' | 'combination' | 'ai_distill'
+export type QuestionIntent = 'informational' | 'evaluative' | 'decisional'
+export type QuestionLayer = 'L1' | 'L2' | 'L3' | 'L4' | 'L5'
+
+export interface QuestionCombinationRequest {
+  region?: string[]
+  prefix?: string[]
+  core: string[]
+  industry: string[]
+  suffix?: string[]
+  max_items?: number
+}
+
+export interface QuestionDistillRequest {
+  seed_topic: string
+}
+
+export interface QuestionCandidate {
+  text: string
+  layer: QuestionLayer
+  intent: QuestionIntent
+  source: QuestionSource
+  missing_suffix?: boolean
+  too_short?: boolean
+  duplicate?: boolean
+  suggest_skip?: boolean
+}
+
+export interface QuestionCandidateResult {
+  candidates: QuestionCandidate[]
+  ai_points_charged?: number
+  cache_hit?: boolean
+  truncated?: boolean
+}
+
+export interface ClassifiedQuestion {
+  text: string
+  layer: QuestionLayer
+  intent: QuestionIntent
+}
+
+export interface MaterializeQuestion {
+  text: string
+}
+
+export interface MaterializeQuestionsRequest {
+  source: QuestionSource
+  questions: MaterializeQuestion[]
+}
+
+export interface SkipReason {
+  text: string
+  reason: string
+}
+
+export interface MaterializeQuestionsResult {
+  created_questions: number
+  skipped_questions: SkipReason[]
+}
+
+export interface ClassifyQuestionsRequest {
+  texts: string[]
 }
 
 export interface CompetitorRequest {