Security fixes from deep review:
- Add input validation patterns for project_id, agent_id, collection
- Add path traversal protection for source_path (reject .., null bytes)
- Add error codes (INTERNAL_ERROR) to generic exception handlers
- Handle FieldInfo objects in validation for test robustness
Performance fixes:
- Enable concurrent hybrid search with asyncio.gather
Health endpoint improvements:
- Check all dependencies (database, Redis, LLM Gateway)
- Return degraded/unhealthy status based on dependency health
- Updated tests for new health check response structure
All 139 tests pass.
- Wrap store_embeddings_batch in transaction for all-or-nothing semantics
- Add replace_source_embeddings method for atomic document updates
- Update collection_manager to use transactional replace
- Prevents race conditions and data inconsistency (closes#77)
