Allow configuring available languages from helm chart

[emma-sg]

Closes #2223

• Adds localesAvailable to /api/settings endpoint, and uses that list if available, rather than the full list of translated locales, to determine which options to display to users
• Uses the user's browser locales, filtered to the current language setting, for formatting numbers, dates, and durations
• Adds & persists checkbox for "use same language for formatting dates and numbers" in user settings
• Replaces uses of sl-format-bytes with localize.bytes(...), and sl-format-date with replacement btrix-format-date that properly handles fallback locales
• Caches all number/duration/datetime formatters by a combined key consisting of app language, browser language, browser setting, and formatter options so that all formatters can be reused if needed (previously any formatter with non-default options would be recreated every render)
• Splits out ordinal formatting from number formatter, as it didn't make much sense in some non-English locales
• Adds a little demo of date/time/duration/number formatting so you can see what effect your language settings have

Screen.Recording.2024-12-12.at.7.09.32.PM.mov

[emma-sg]

Documenting this in case it comes up again: for whatever reason we were getting CORS errors in Playwright trying to call API endpoints that were proxied, which caused the page to never complete loading. Adding changeOrigin: true to the createProxyMiddleware configs fixed this in 147dd13.