v0.8.0 - Helm chart + chart.js + alerts + detect-agents

Highlights

• Helm chart for k8s deployments
• Dashboard time-series chart (chart.js stacked bar with 1h/6h/24h/3d/7d selector)
• agentgate alerts - YAML alert engine with time windows + thresholds
• agentgate detect-agents - auto-detect installed AI agents

Bug fixes

• counts_per_bucket SQL was splitting buckets per microsecond. Now uses CAST(... AS INTEGER).
• since_within returned dict with column indices off-by-one. Now correctly maps to actual events schema.

Tests

• Added tests/test_alerts.py (4 tests)
• Added tests/test_dashboard.py (3 tests)
• 92/92 tests passing