refactor(frontend): Mantine Component Library PoC

[Akuukis]

🗒️ Checklist

1. run linter locally
2. update all related docs (API, README, inline, etc.), if any
3. draft PR with a title <type>(<scope>)<!>: <title> TASK-1234
4. tag PR: at least frontend or backend unless it's global
5. fill in the template below and delete template comments
6. review thyself: read the diff and repro the preview as written
7. open PR & confirm that CI passes
8. request reviewers, if needed
9. delete this section before merging

💭 Notes

Please read the PR commit-by-commit, here's a guide.

1. 3105f47 Setup Mantine Component Library. Please install the new dependencies, and add recommended VSCode extensions.
2. 453f2c1 Here's a preview that Mantine in general works, and API for the example Button is different but generally similar.

our button	Mantine default button

3. d782e38 Example of custom styled component, Button. IMHO achieves pixel-perfect match in storybook and example above, except for line breaks, spinner and hover animations. Click animation matches out of box. Icon-only buttons are omitted because Mantine uses a different component IconAction for those.

Original on left / Mantine implementation on right

5. eaf45e3 Wrapped Button to add support for inbuilt Tooltip. No idea if we want to move forward with these two coupled, but I found it useful for comparison by re-implementing part of old Button behavior that's represented in storybook.

Original	Mantine implementation

👀 Preview steps

1. ℹ️ open Kobo home
2. 🟢 [on main] notice the original "new" button
3. 🟢 [on PR] notice the new "new" button with default mantine style, only slightly different

[p2edwards]

looks nice so far!

• i like the preview, including how simple this diff is:
  
• haven't test locally yet w/ vscode extensions.
• it's cool that Mantine's PostCSS plugin didn't require modifying webpack.

future stuff:

• curious about a vanilla extract example, usage and setup, its impact on build speed and jest test environments. i'm confident a good solution can be found, though, both to get it working and to separately optimize it if we need to.