feat(i18n): add config.supportedLanguages to filter and order UI language list

[iospro]

Summary

• Added config.supportedLanguages option to restrict and reorder the language list shown in UI settings
• Introduced supportedLanguages.ts as the single source of truth for all language constants
• Language filtering works correctly on both web (static init) and native (reactive via Redux)

Changes

File	Details
config.js	Added // supportedLanguages: ['en', 'ru', 'de'] option near defaultLanguage
configType.ts	Added supportedLanguages?: Array<string> to IConfig
base/i18n/supportedLanguages.ts	New file: exports LANGUAGES (all) and SUPPORTED_LANGUAGES (filtered by config)
base/i18n/i18next.ts	Re-exports from supportedLanguages.ts; whitelist uses [DEFAULT_LANGUAGE, ...SUPPORTED_LANGUAGES]
base/i18n/languageDetector.web.ts	Uses LANGUAGES for case normalization only; filtering delegated to i18next whitelist
base/i18n/languageDetector.native.ts	Uses LANGUAGES for locale detection (consistent with web)
base/i18n/functions.any.ts	Added getSupportedLanguages(state) Redux selector
settings/components/native/LanguageSelectView.tsx	Uses useSelector(getSupportedLanguages) for reactive language list on native
settings/functions.any.ts	Uses SUPPORTED_LANGUAGES for web language selector

How it works

Web: window.config is available before the JS bundle loads → SUPPORTED_LANGUAGES is correctly computed at module init time → used directly in i18next whitelist and settings UI.

Native: config arrives via Redux after connecting → getSupportedLanguages(state) selector reads config.supportedLanguages reactively → LanguageSelectView re-renders with the correct filtered list.

Responsibilities:

Layer	Responsibility
supportedLanguages.ts	Compute filtered list from window.config (web)
i18next whitelist	Enforce allowed languages in i18next engine
Language detectors	Normalize/detect only — no filtering
getSupportedLanguages selector	Filter for native UI from Redux state

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.