Add French (fr) translation

[ADNPolymerase]

Summary

Adds a complete French (fr) translation, mirroring the existing en and pl files.

• New file: custom_components/worx_vision_cloud/translations/fr.json
• Same JSON structure and keys as en.json / pl.json (171 keys, validated identical)
• Covers the config flow (login step, errors, abort) and all entity names (lawn_mower, sensor, binary_sensor, switch, button, number, select, update, camera, calendar)

Notes

• Translations are natural French, not literal — e.g. Save the hedgehogs → Mode hérissons, Party mode → Mode festif, Smart edge cutting → Coupe de bordure intelligente.
• No other files needed changes: Home Assistant auto-detects translation files by filename in the translations/ folder, and there is no strings.json in this integration.