feat(i18n): implement localization foundation (Russian) and phased rollout

[CatSema]

Add Vue I18n infrastructure with a locale registry, browser/system locale detection, user language override in preferences, Quasar language synchronization, modular locale domains, and UI localization across core and high-traffic functional areas.

Also add i18n documentation, validation/check tooling, and related cleanup needed for rollout readiness.

Some hardcoded user-facing strings may still remain in low-traffic paths, but this PR establishes the baseline architecture and workflow for incremental completion.

Notes

AI was used as an assistance tool while preparing this PR.

All proposed changes were reviewed manually and tested in a development/non-production environment before submission.

In addition, a modified internal build that includes this work has already been used on a regular basis within our organization, which helped validate the changes in real-world usage scenarios.

The final PR content was reviewed and adjusted manually before submission.

[CLAassistant]

All committers have signed the CLA.

[wh1te909]

hi, the frontend is undergoing a significant rewrite, so this needs to wait until it’s complete, then be rebased and any merge conflicts resolved.

[CatSema]

hi, the frontend is undergoing a significant rewrite, so this needs to wait until it’s complete, then be rebased and any merge conflicts resolved.

Understood, thank you. I’ll wait for the frontend changes before adapting this PR further.
Do you have an approximate timeline for when those changes are expected?

[CatSema]

Hi @wh1te909 !

Do you have any rough ETA for the frontend rework?

[CatSema]

Hi @wh1te909 , just checking in on this PR.

Is the frontend rewrite still in progress, or should I start rebasing and adapting this PR to the current develop branch?

I’m happy to update it when the frontend changes are ready.