Fix: Push notifications error on unsupported browsers

[sentry]

Description

This PR addresses the unhandled error "Push messaging is not supported in this browser." (SABLE-TQ) that occurred when enablePushNotifications() was called on browsers lacking serviceWorker or PushManager APIs.

Root Cause:

1. The togglePusher() function, invoked on every visibilitychange event, called enablePushNotifications() without first checking for browser push notification capability.
2. enablePushNotifications() would then throw an unhandled error if the necessary browser APIs (serviceWorker, PushManager) were absent.
3. The usePushNotifications setting could be enabled (and defaulted to true on mobile) even on browsers that do not support push notifications (e.g., DuckDuckGo, Safari iOS, Firefox iOS), leading to repeated errors.

Changes Made:

1. Introduced isPushSupported() utility: A new helper function isPushSupported() was added to PushNotifications.tsx to check for the presence of serviceWorker and PushManager APIs.
2. Guarded togglePusher(): togglePusher() now performs an early return if !isPushSupported(), preventing calls to enablePushNotifications() on unsupported browsers and eliminating the repeated errors on visibility changes.
3. Graceful enablePushNotifications(): The enablePushNotifications() function now returns gracefully instead of throwing an error when push is unsupported, providing a defense-in-depth mechanism.
4. Updated default setting value: The default value for usePushNotifications in settings.ts now includes a check for isPushSupported(), ensuring that the setting is not enabled by default on unsupported browsers.
5. Hid settings UI: The "Background Push Notifications" setting tile in SystemNotification.tsx is now hidden if the browser does not support push notifications, improving the user experience by not presenting unavailable features.

Fixes SABLE-TQ

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).

Fixes SABLE-TQ

[github-actions]

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[github-actions]

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Status	Preview URL	Commit	Alias	Updated (UTC)
✅ Deployment successful!	https://pr-868-sable.raspy-dream-bb1d.workers.dev	e9dbda2	pr-868	Tue, 19 May 2026 10:47:06 GMT

[dozro]

PR by sentry? huh?

[7w1]

bad bot at the very least pr opener needs to be human

[dozro]

bad bot at the very least pr opener needs to be human

Yeah would be preferable lol