feat: Adds support for ntfy's phone call feature

[erik-ff]

Sends X-Call header with either yes or a specific number. These numbers need to be validated in the ntfy dashboard before they can be used.

Note: This feature is only available for Supporter+

https://ntfy.sh/docs/publish/#phone-calls

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📝 Summary of changes done and why they are done

📋 Related issues

• Relates to #issue-number
• Resolves #issue-number

📄 Checklist

Please follow this checklist to avoid unnecessary back and forth (click to expand)

• ⚠️ If there are Breaking change (a fix or feature that alters existing functionality in a way that could cause issues) I have called them out
• 🧠 I have disclosed any use of LLMs/AI in this contribution and reviewed all generated content.
  I understand that I am responsible for and able to explain every line of code I submit.
• 🔍 My code adheres to the style guidelines of this project.
• ⚠️ My changes generate no new warnings.
• 🛠️ I have reviewed and tested my code.
• [ x] 📝 I have commented my code, especially in hard-to-understand areas (e.g., using JSDoc for methods).
• [ x] 🤖 I added or updated automated tests where appropriate.
• [ x] 📄 Documentation updates are included (if applicable).
• [ x] 🔒 I have considered potential security impacts and mitigated risks.
• [ x] 🧰 Dependency updates are listed and explained.

📷 Screenshots or Visual Changes

• UI Modifications: Highlight any changes made to the user interface.
• Before & After: Include screenshots or comparisons (if applicable).

Event	Before	After
UP
DOWN
Certificate-expiry
Testing

[CommanderStorm]

Thank you ❤️

[erik-ff]

No problem! Ended up having to use pager duty anyway, but I figured I'd push this up to y'all instead of keeping it on our fork :)

[CommanderStorm]

thanks