[Feature] Language switch button

**Tl;dr: Implement language switch button.**

Users currently have to manipulate the link in the address bar to change the interface language, e.g. for French:
https://ground.openforis.org/en/surveys --> https://ground.openforis.org/fr/surveys

Please place a language switch button at the top right, using the same standard [Google icon](https://fonts.google.com/icons?selected=Material+Symbols+Outlined:translate:FILL@0;wght@400;GRAD@0;opsz@24&icon.query=language&icon.size=24&icon.color=%231f1f1f) as in Ground Android. Please display language names in the respective language (not "French" but "Français", not "Spanish" but "Español", etc...). See example sketch below:

@rfontanarosa @kenstershiro