feat: comprehensive governance dashboard

[temper-pulseengine]

Summary

• Add root / redirect to /dashboard
• Tab navigation: Repositories, Policy Config, Issues
• Compliance score card (percentage across 5 governance dimensions)
• Policy Config tab showing all rules from config.yml: merge strategy, branch protection, auto-merge, labels
• Enhanced repo table with signed commits, auto-merge, dependabot, labels columns
• Issues tab with grouped-by-repo drift detection
• 5-minute in-memory cache for GitHub API responses

Test plan

• Verify / redirects to /dashboard
• Verify all three tabs render correctly
• Verify policy config reflects config.yml settings
• Verify repo table shows all 19 repos with correct status badges
• Verify issues tab shows "All repos compliant" when no drift

🤖 Generated with Claude Code