MVP: End-to-end integration test

[acgetchell]

Description

Create end-to-end test that validates full workflow.

Tasks

• Upload test PDF via frontend
• Verify job queued in Cloudflare Queue
• Confirm controller picks up job
• Validate SLURM job submission
• Check job completion and results
• Verify results available via status API

Acceptance Criteria

• Complete upload → process → result flow works
• All components communicate correctly
• Test can be run repeatedly for CI/CD