- Added comprehensive load tests for upload endpoints:
* Concurrent simple uploads (20 concurrent uploads)
* Concurrent chunked uploads (5 uploads with 10 chunks each)
* Chunked upload stress test (10 uploads with 20 chunks each)
* Upload status polling under load (50 concurrent polls)
- All tests measure throughput, success rates, and response times
- Tests use in-memory SQLite and Redis (if available) for fast execution
- All tests tagged with load build tag
