Desktop,Mobile: Update Mermaid to v10.9.1

[personalizedrefrigerator]

Summary

This pull request upgrades mermaid.js to version 10.9.1 from 10.6.1. See the mermaid releases page for a list of changes.

Testing plan

1. Create a new note with the following content:

   ```mermaid
   graph LR
       A[$$n$$]
       B["$$n \over 2$$"]
       C["$$\frac{n}{2}$$"]
       A--"$$\mathcal{O}(1)$$"-->B
       A--"$$\mathcal{O}(1)$$"-->C
   ```
   

2. Verify that the flowchart renders (and that the math also renders):
   
3. Desktop only:
   1. Download a copy of the diagram using the download button and attach it to the note.
   2. Switch to the rich text editor.
   3. Verify that the original diagram and the attached SVG export render.

This has been tested successfully on Ubuntu 24.04 (desktop) and on an Android 12 emulator (mobile).

[personalizedrefrigerator]

Temporarily converting to a draft — there's an issue with math typesetting in diagrams caused by a use of white-space: pre in Joplin. Edit: The sequence diagram example was rendering incorrectly (some text missing). This has been fixed.

[sysescool]

nice! thanks a lot. so that I can use new diagram type block-beta.