Enable fullscreen video on macOS

[Ujjwal5705]

Problem

On macOS, videos embedded in Zulip Desktop could not enter fullscreen mode.
This was caused by the app’s permission handler not explicitly granting the fullscreen permission.

Solution

Updated the ipcRenderer.on("permission-request") handler to grant fullscreen permission in addition to existing ones (e.g., notifications).
This ensures video players and other elements can properly request fullscreen.

Fixes: #1409

Screen Capture:-

Screen.Recording.2025-09-14.at.5.46.14.PM.mov

Embedding Check:-

Screen.Recording.2025-09-14.at.6.18.38.PM.mov

Platforms Tested

• Windows
• macOS
• Linux

Self-review checklist

• Code changes are minimal and scoped to permission handling.

• Commit message explains the fix clearly.

• Verified fullscreen works on macOS video players (tested on YouTube and Zulip-embedded media).

• Tested on Windows/Linux to confirm no regressions.

[zulipbot]

Hello @Ujjwal5705, it seems like you have referenced #1409 in your pull request description, but you have not referenced them in your commit message description(s). Referencing an issue in a commit message automatically closes the corresponding issue when the commit is merged, which makes the issue tracker easier to manage.

Please run git commit --amend in your command line client to amend your commit message description with Fixes #1409..

An example of a correctly-formatted commit:

commit fabd5e450374c8dde65ec35f02140383940fe146
Author: zulipbot
Date:   Sat Mar 18 13:42:40 2017 -0700

    pull requests: Check PR commits reference when issue is referenced.

    Fixes #51.

To learn how to write a great commit message, please refer to our guide.

[alya]

Please clean up your commit history and post again to request a review. See here for guidelines.

[Ujjwal5705]

@alya I’ve cleaned up the commit history as per the guidelines and updated the branch. Could you please take another look?