[Test] Add E2E Tests for Complete Emergency Workflow #13

Problem

Integration tests exist but no true end-to-end tests for full workflow.

Workflow to Test

1. Create emergency request
2. Find nearby donors
3. Run matching
4. Reserve inventory
5. Send notifications
6. Record saga events
7. View analytics

Solution

Create comprehensive E2E test suite covering:

• Happy path (full success)
• Partial failures (recovery)
• No inventory scenario
• No donors scenario

Acceptance Criteria

• Happy path test passes
• Tests in tests/integration/
• All services involved tested
• Takes < 10 seconds