feat(web): add generic webhook as notification service option

[s0up4200]

Summary

• Adds "Generic Webhook" as a selectable notification service type in the notification settings UI
• Uses the Shoutrrr generic:// URL scheme which was already supported by the backend but missing from the frontend dropdown

Closes #125

Test plan

• Navigate to Settings > Notifications
• Create a new notification channel
• Verify "Generic Webhook" appears in the service type dropdown
• Verify the example URL shows generic://HOSTNAME/PATH?template=json
• Test sending a notification to a generic webhook endpoint

Summary by CodeRabbit

Release Notes

• New Features

  • Added Generic Webhook as a new notification service option.

• Bug Fixes

  • Corrected the Pushover service configuration example format.

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[s0up4200]

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📝 Walkthrough

Walkthrough

Added Generic Webhook as a selectable notification service option in the UI notification settings to match shoutrrr's backend support. Updated the Pushover service example URL format by removing an extraneous colon in the token portion.

Changes

Cohort / File(s)	Summary
Notification Services Configuration web/src/api/notifications.ts	Added Generic Webhook service option (value: "generic", label: "Generic Webhook", example: "generic://HOSTNAME/PATH?template=json"). Fixed Pushover example format by removing leading colon in token portion.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• fix(web): remove extra colon in Pushover notification example #168: Applies the same Pushover example URL fix (removing the extra colon) to align the documentation with correct service URL formatting.

Poem

🐰 A webhook generic, now ready to hop,
Through notification tunnels without any stop,
Pushover's format cleaned up with care,
Local webhooks answered—fair and square! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: adding a generic webhook notification service option to the web UI.
Linked Issues check	✅ Passed	The pull request successfully addresses issue #125 by adding 'Generic Webhook' as a selectable service type in the notification settings dropdown.
Out of Scope Changes check	✅ Passed	All changes are in-scope: the new Generic Webhook entry and the Pushover example fix are directly related to notification service configuration.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

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