[codex] add mobile attention notifications

[tehao999]

Summary

• add mobile attention notifications for permission requests, ready transitions, and failure/interruption events
• switch web push subscription to explicit settings-driven enable/resubscribe flows and clean up failed registrations
• harden notification click routing and add coverage for Codex failure events, service worker routing, and notification settings flows

Test Plan

• bun run test
• bun run typecheck
• bun run build:web