Implement Nightly Integration Tests

[chrsoo]

Priority: Low
Labels: ci-cd, area:testing, priority:low, automation

Description:
Run comprehensive integration tests nightly to catch regressions early.

Source: Item #50 from consolidated analysis
Files: CI configuration

Acceptance Criteria:

• Nightly test schedule configured
• Full test suite runs
• Results reported to team
• Failure notifications
• Test history tracking

Related Issues: #27 (Test Coverage), #39 (CI Integration)