refactor: improve push notification received utils

[Prithpal-Sooriya]

Explanation

We are throwing an error when subscribing the the push notification background listener. Instead we shall fail silently.
I've also added TODOs for areas to improve for push notifications

1. Using an open-api typed end-to-end schema shared with backend and frontend. Should sync what marshalled data our backend is pushing to clients in the data payload.
2. Migrate the handler and push notification logic to use the shared Notification push payload used in mobile. This handler can then just be responsible for analytics and not actual push logic.

References

https://consensyssoftware.atlassian.net/browse/ASSETS-1857

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

---

Note

Harden web push notification utilities with defensive parsing and silent failure, remove legacy service-worker module, and update tests and changelog.

• Web push utilities (web/push-utils.ts):
  • Make listenToPushNotificationsReceived handler optional and guard against unsupported Firebase.
  • Parse payload defensively (JSON.parse(... ?? 'null')), validate with isOnChainRawNotification, and process via safeProcessNotification with early returns on invalid data.
  • Stop throwing on errors; log via log.error instead.
  • Keep click handling and subscription creator, publishing messenger events as before.
• Removals:
  • Delete legacy service worker implementation and tests: services/push/push-web.ts and services/push/push-web.test.ts.
• Tests:
  • Update web/push-utils.test.ts to cover invalid payload cases and adjusted handler behavior; remove error-throw assertions.
• Docs/Meta:
  • Update CHANGELOG.md to note background push utilities now handle more edge cases without throwing.

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[Prithpal-Sooriya]

Removing as these are never used or ever exported. It is safe to remove without introducing a breaking change.

[Prithpal-Sooriya]

https://consensyssoftware.atlassian.net/browse/ASSETS-1909