E1: In-App Notification Centre

[ShortCipher5]

Persistent in-app notification tray giving users visibility into all background deployment and resource events.

References: PRD §6.1, §6.3

Acceptance Criteria

• Bell icon in top nav bar with unread count badge
• Clicking bell opens notification tray
• Each entry: event type label, container + environment name, commit message + short SHA (deploy events), relative timestamp (absolute on hover)
• Primary action button contextual to event: deploy.failed → "View Error" | deploy.succeeded → "Open App" | redeploy.triggered → "View Progress"
• Entries marked read on click or primary action
• Unread state persists across sessions
• Retention: 30 days