VS-18 — Risk Alerts Notification Badge #67

What to build

A persistent notification badge in the app navigation showing the count of unseen risk alerts, backed by a live Firestore listener on the risk_alerts collection — the same source used by VS-10's dashboard activity panel. No real push notifications (this is a website, not a native app): just an in-app badge + list.

Acceptance criteria

• Badge on the navigation icon shows the count of risk_alerts documents with detected_at more recent than users/{uid}.last_seen_alert_at
• Badge updates live via onSnapshot — no polling
• Opening the alerts list marks currently-visible alerts as seen by writing users/{uid}.last_seen_alert_at
• Badge count resets to 0 once alerts are seen
• No browser/OS push notifications — explicitly out of scope

Blocked by

VS-10 Dashboard Vertical Slice v1 (KPI + Activity + Map Summary)