feat: enhance asset import functionality and unit tracking

- Added WHISPER_URL environment variable to docker-compose for audio transcription service.
- Updated Nginx configuration to increase timeout settings for API requests.
- Enhanced asset ingestion process to extract unit numbers from ZIP entry paths, supporting various naming conventions.
- Implemented logic to split intensive courses into two regular courses during asset import.
- Added new fields to the Asset and QuestionBank models to track unit numbers and source asset links.
- Introduced backward-compatible fallbacks for fetching study plans and courses from legacy MySQL database.
- Improved error handling and progress tracking during ZIP file uploads in the frontend.
- Created a new SQL migration to add unit_number and source_asset_id columns to the assets and question_bank tables, along with necessary indexes for performance.

services/cms-service/migrations/20260407000000_add_unit_asset_link.sql

@@ -0,0 +1,12 @@
+-- Add unit_number to assets: tracks which syllabus unit a file belongs to within a ZIP
+ALTER TABLE assets ADD COLUMN IF NOT EXISTS unit_number INTEGER;
+
+-- Link question_bank RAG chunks to their source audio/video asset
+-- This allows test creation (AI + manual) to attach the audio to exercises
+ALTER TABLE question_bank ADD COLUMN IF NOT EXISTS source_asset_id UUID REFERENCES assets(id) ON DELETE SET NULL;
+ALTER TABLE question_bank ADD COLUMN IF NOT EXISTS unit_number INTEGER;
+
+-- Index for fast lookup by unit
+CREATE INDEX IF NOT EXISTS idx_assets_unit_number ON assets(organization_id, sam_plan_id, unit_number);
+CREATE INDEX IF NOT EXISTS idx_qb_source_asset ON question_bank(source_asset_id) WHERE source_asset_id IS NOT NULL;
+CREATE INDEX IF NOT EXISTS idx_qb_unit_number ON question_bank(organization_id, unit_number) WHERE unit_number IS NOT NULL;