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.

deploy/config.yaml

@@ -132,6 +132,11 @@ membership:
 brand_library:
   free_brand_limit: 1
   paid_brand_limit: 2
+  question_limits_by_plan:
+    default: 25
+    free: 5
+    plus: 25
+    pro: 50
   max_keywords: 5
   max_questions_per_keyword: 5
 

deploy/k3s/config/config.yaml

@@ -88,6 +88,11 @@ membership:
 brand_library:
   free_brand_limit: 1
   paid_brand_limit: 2
+  question_limits_by_plan:
+    default: 25
+    free: 5
+    plus: 25
+    pro: 50
   max_keywords: 5
   max_questions_per_keyword: 5