Core search endpoint using PostgreSQL trigram similarity.
Acceptance Criteria:
- GET /api/v1/hs-codes/?q=chicken returns relevant results
- Searches both hs_code and description fields
- Similarity threshold 0.1 tunable via env var
- Results ordered by similarity score descending
- Returns empty list not 404 when no results
- Returns 400 if q param is missing
Core search endpoint using PostgreSQL trigram similarity.
Acceptance Criteria: