[FEATURE] Add Russian (ru) to the display-language options of Claude apps (Desktop / claude.ai / Code UI)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet — the closest one is #50680 (auto-closed as inactive and locked by stale-bot; per its lock message, opening this renewed request)
• [x] This is a single feature request (not multiple features)

Problem Statement

Claude apps currently offer 11 display languages (English, French, German, Hindi, Indonesian, Italian, Japanese, Korean, Brazilian Portuguese, Latin-American Spanish, Spanish). Russian is missing, while millions of developers across the CIS and Central Asia use Russian as their daily working language — I'm a freelance developer in Tashkent, Uzbekistan, and Russian is my primary working language for clients, docs, and communication.

Claude already converses fluently in Russian, so the only thing left in English is the UI chrome (menus, settings, hints, dialogs) in Claude Desktop, claude.ai, and the Code UI. The result is a jarring mixed-language experience for Russian-speaking users.

Proposed Solution

Add Русский (ru) to the existing display-language selector (Settings → Language). The localization infrastructure already exists — this is an incremental addition to the current 11 languages, not a new i18n framework.

Alternative Solutions Considered

• Community patches (e.g., patching the Electron app.asar, the way warment/zcode-ru does for Z.ai's ZCode desktop app) — not viable for Claude, since the Claude Desktop UI is served from claude.ai rather than bundled locally, and the CLI updates too frequently for a patch to survive.
• Relying on model responses in Russian (language setting) — covers content, not UI chrome.

Additional Context

Happy to test pre-release builds and review translation quality.

Environment: Claude Desktop 1.40609.0 (macOS 25.6.0, arm64), Claude Code 2.1.250.