feat: Re-enable machine translations

[AyakorK]

🎩 Description

Configures DeepL as the machine translation service using Decidim's built-in machine translation framework.

The DeepL API key is read from the DEEPL_AUTH_KEY environment variable (free accounts use a :fx suffix). Machine translations can be toggled per-organisation via the admin settings, and globally via DECIDIM_MACHINE_TRANSLATIONS_ENABLED.

✅ Testing

Setup

1. Add your DeepL API key to your .env: DEEPL_AUTH_KEY=your_key_here
2. Add DECIDIM_MACHINE_TRANSLATIONS_ENABLED=true to your.env.
3. Enable machine translations on the organisation: Admin → Settings → Configuration → Check Enable machine translations
4. Make sure Sidekiq is running and consuming the translations queue

Test

1. Create or edit translatable content (proposal, comment, participatory process…) in one language
2. Switch the interface language
3. The translated content should appear automatically

📌 Related Issues

• Fixes https://github.com/orgs/OpenSourcePolitics/projects/26/views/1?filterQuery=assignee%3AAyakorK&pane=issue&itemId=196382177&issue=OpenSourcePolitics%7Cintern-tasks%7C453

Tasks

• Add specs
• Add DeepL
• Configure env vars for machine translations
• Add locales