Opt-in/Opt-out UI: improve French copy and align all locales to clear German source text

[emernual]

The team at ch.ch is using Matomo’s standard plugin for opt-in/opt-out.

-They are satisfied with the German version of the default text, which is clear and detailed.
-In other languages, especially French, the text is harder to understand.
-They propose an alternative French wording: "Votre navigation est suivie. Décochez cette case pour exclure le suivi."
-Ideally, they suggest translating the German text directly into other languages to maintain clarity:
"Ihr Besuch dieser Webseite wird aktuell von der Matomo Webanalyse erfasst. Diese Checkbox abwählen für Opt-Out."
-They request that Matomo update/adapt the standard text in other languages accordingly.

[sgiehl]

Hey @emernual,

Our translations are all community contributed. So in case there are improvements suggested, they can simply be applied on weblate. Feel free to also suggest them to create an account there in order to provide translations:
https://hosted.weblate.org/projects/matomo/