Migrate appSettings and userSettings to TypeScript

[terite]

In an attempt to keep code changes minimal, I added some FIXME comments to relevant places instead of changing behavior.

Changes

• Migrate AppSettings to TypeScript
• Migrate UserSettings to TypeScript
• Remove the UserSettings.getData method
• Remove the UserSettings.importFrom method

Issues

[sonarqubecloud[bot]]

Quality Gate passed

The SonarCloud Quality Gate passed, but some issues were introduced.

4 New issues
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[jellyfin-bot]

This pull request has merge conflicts. Please resolve the conflicts so the PR can be successfully reviewed and merged.

[terite]

I'm not sure what's up with eslint. Locally my npm run lint has no errors (but 39 warnings, mostly not these files). I'll wait for feedback before continuing further there.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
14 New issues

Measures
0 Security Hotspots
No data about Coverage
0.6% Duplication on New Code

See analysis details on SonarCloud

[jellyfin-bot]

Cloudflare Pages deployment

Latest commit	8e71295
Status	✅ Deployed!
Preview URL	https://c9fdf9f3.jellyfin-web.pages.dev
Type	🔀 Preview

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[jellyfin-bot]

This pull request has merge conflicts. Please resolve the conflicts so the PR can be successfully reviewed and merged.

[thornbill]

Hey @terite! Now that 10.9 is finally out the door, could you update this branch and we'll get it merged? Thanks!