chore(i18n): French translation improvements

[fturmel]

Description

see #6406 for the changes against beta

• The apostrophe character ’ should be used instead of the single quote '
• Gender corrections: "L’adresse e-mail fournie", "Vérification échouée"
• Lowercase: "Supprimer le téléversement"
• Dark and light theme: I think it makes more sense to use "Sombre" and "Clair" here to identify the theme. Day/Night modes imply a hue/warmth correction and are different features altogether. Reference: https://fr.wikipedia.org/wiki/Mode_sombre#Mode_sombre_et_mode_nuit_ou_chaud
• Fix accent: "Mis à jour avec succès"
• "Bienvenue" I think would be the correct standalone greeting form. Reference: https://www.projet-voltaire.fr/question-orthographe/orthographe-bienvenu-bienvenue-chez-moi/
• "Recadrer" is the correct word for "crop". "Récolte" means "crop" in the sense of "harvest", so this was probably a bad literal Google Translate that slipped through.
• Correct all "Es-tu sûr ?" to the proper formal "Êtes-vous sûr ?" for consistency
• Use article défini since we will enumerate the values: "Ce champ contient les sélections invalides suivantes :"
• Space before question marks

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• I have read and understand the CONTRIBUTING.md document in this repository.

Type of change

• Chore (non-breaking change which does not add functionality)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Change to the templates directory (does not affect core functionality)
• Change to the examples directory (does not affect core functionality)
• This change requires a documentation update

Checklist:

• I have added tests that prove my fix is effective or that my feature works
• Existing test suite passes locally with my changes
• I have made corresponding changes to the documentation