v0.15.8

v0.15.8 — Grafana Dashboard Modernization

6 dashboard enhancements:

• Consolidated to single source-of-truth dashboard file
• Fixed Nemo iframe URL placeholder
• Added 30-day Probe Dropout / ±4σ Anomaly / Tank Events annotations
• Added custom time picker (30d/90d presets)
• Converted Log Viewer to log stream panel with custom date format
• Cleaned up duplicate dashboards in Grafana