Take the list of languages into account dynamically

[Otaku17]

Description

This PR introduces a more robust i18n system that separates active and inactive languages using a new format in package.json.
The updated structure allows finer control over which translation files are loaded into the application and ensures the JSON files remain in sync.

Close #499

Changes include:

• package.json now defines languages as an object with boolean values ({ "fr": true, "de": false, ... })
• i18n updater script:
  • Updates or creates .json files for all referenced languages.
  • Loads and syncs only languages marked true.
  • Skips loading languages marked false but still creates or updates their .json files.
  • Deletes .json files not listed in package.json.
• Frontend i18n config:
  • Dynamically loads only the active (true) language files.
  • Ensures en.json is always used as the fallback.

Note before testing

Make sure package.json contains the new languages format:

"languages": {
  "en": true,
  "fr": true,
  "de": false,
  ...
}

Tests to perform

• Confirm that only languages marked as true in package.json are loaded at runtime.
• Verify that all translation files (both true and false) are correctly created and synchronized with en.json.
• Ensure that any .json files not listed in package.json are removed.
• Temporarily change a language from false to true and verify it begins loading correctly.
• Confirm that no error is thrown if a false language file exists but is not loaded.