feat: migrate app strings to i18n JSON namespaces from 4.11.1

[Vad0kVad0k]

Summary

• move hardcoded UI strings across the app to i18n keys
• split translations into feature-based JSON namespaces for en and ru
• wire updated translation usage in components/hooks/pages to the new localization architecture

Why

This reduces string duplication, makes translations easier to maintain, and prepares the codebase for adding more locales with less friction.

Notes

• includes broad updates across settings, room/message flows, auth, and shared UI
• no intended behavior changes beyond localization source migration

Test plan

• run app and verify main navigation, room view, settings, and auth pages render translated text
• switch language between en and ru and verify key screens keep parity
• check message-related UI (timeline, reply, upload/media viewers) for missing i18n keys
• check browser console for translation lookup warnings/errors

[github-actions]

Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

---

I have read the CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.}

[Vad0kVad0k]

I have read the CLA Document and I hereby sign the CLA