fix(web): do not play memory video if the MemoryVideoViewer element is not visible

[Zlendy]

Description

Clicking on a gallery video while having a memory video open can start a double playback in certain situations.
This happens because the code responsible for auto playing/pausing the memory video doesn't check if the element is visible.

To fix it, I used the Element.checkVisibility() method. This Web API is currently "Newly available", however, I couldn't find a FAQ entry or contributing guideline regarding the usage of newly added Web APIs.

I don't think it would be an issue considering that it is supported by 93.39% of browser installations according to caniuse, but wanted to disclose it anyway.

How Has This Been Tested?

1. Open a memory containing a video (memory video starts playing)
2. Scroll down to the gallery (memory video stops playing)
3. Click on a video in the gallery (with my patch the memory video doesn't start automatically, without it, it does)

Screenshots (if appropriate)

Checklist:

• I have carefully read CONTRIBUTING.md
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if applicable
• I have no unrelated changes in the PR.
• I have confirmed that any new dependencies are strictly necessary.
• I have written tests for new code (if applicable)
• I have followed naming conventions/patterns in the surrounding code
• All code in src/services/ uses repositories implementations for database calls, filesystem operations, etc.
• All code in src/repositories/ is pretty basic/simple and does not have any immich specific logic (that belongs in src/services/)

Please describe to which degree, if any, an LLM was used in creating this pull request.

This code is 100% hand-made.

[immich-push-o-matic]

Label error. Requires exactly 1 of: changelog:.*. Found: 🖥️web. A maintainer will add the required label.