Block notifications from bypassing the user blocking feature on iOS.
Vulnerabilities fixed:
1. Nostr public messages: checkForMentions() was called regardless of
blocking status, allowing blocked users to trigger mention notifications
2. Noise-encrypted DMs: didReceiveNoisePayload() didn't check blocking
before calling handlePrivateMessage(), allowing DM notifications
Changes:
- ChatViewModel+Nostr.swift: Add blocking check before checkForMentions()
and sendHapticFeedback() in subscribeNostrEvent
- ChatViewModel.swift: Add isPeerBlocked() check in didReceiveNoisePayload
before processing private messages
- Add NotificationBlockingTests.swift with 5 tests for blocking behavior
Security: Blocked users can no longer trigger notifications through any
message path (Nostr public, Nostr DM, or BLE Noise DM).
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
