Add Russian localization

[serezha93]

Summary

• add Russian (ru-RU) as a selectable UI language
• add a complete Fluent catalog covering all 712 application locale keys
• wire Russian through the Rust settings model, locale loader, and TypeScript bridge
• add Rust and frontend coverage for language discovery, aliases, bridge payloads, and the settings picker

Why

Win-CodexBar currently offers six UI languages but no Russian option. This adds a native-language experience for Russian-speaking Windows users while preserving the existing English fallback behavior.

Validation

• cargo test --manifest-path rust/Cargo.toml language --no-fail-fast
• cargo test --manifest-path rust/Cargo.toml locale::tests --no-fail-fast
• pnpm run check-locale — 712 keys match between Rust and TypeScript
• pnpm test — 35 files / 211 tests passed
• verified placeholder counts match the English catalog for all 712 keys

Build note

pnpm run tauri:build:debug currently stops on two pre-existing TypeScript errors in main: ProviderUsageSnapshot.localUsage in MenuCardDetails.tsx and a null assignment in providerGridUtils.test.ts. Neither file is changed by this PR.

The catalog is complete; further native-speaker wording refinements are welcome during review.

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[Finesssee]

Thanks for the PR, I will review it ASAP.

[Finesssee]

Thermo-nuclear code-quality review (automated)

Verdict: Approve on code quality. Clean, pattern-faithful localization addition with good coverage.

The wiring is exactly the established per-language pattern — one Language::Russian variant plus one arm appended to each of the four Language match functions (display_name, all, to_string, aliases), one RU_RU LazyLock + match arm in locale.rs::language_id, one union member in bridge.ts, one FALLBACK_LANGUAGE_OPTIONS entry, and parallel test coverage across all three test files. Nothing leaked into a shared path; no scattered special-casing; no new abstraction. bridge.ts's "russian" stays aligned with Rust to_string(). The new ru-RU.ftl (713 lines / 712 keys) has no duplicate keys, no malformed Fluent lines, and mirrors the English catalog's (unusual but established) { "{}" } literal-brace placeholder convention exactly — e.g. PredictivePaceWarningTitle = { "{}" {} pace warning vs { "{}" } { "{}" } предупреждение о темпе. The fallback-completeness test now includes ru-RU, so the "English is a superset / others fall back" invariant is preserved. The catalog line count is inherent data, not a >1k-logic-file smell.

Nits (non-blocking):

• settings/types.rs: the four per-language match fns (display_name / all / to_string / aliases) are O(n)-arms per language — a future data-table (lang, code, display, aliases) would collapse all four into one and make adding an 8th language a one-line edit. That's a refactor of pre-existing structure across all 6 existing languages, not this PR's job — flagging only as optional future cleanup, not a blocker.
• GeneralTab.test.tsx: the test was renamed to renders all supported language options but still asserts toHaveLength(7) — a hardcoded count. If the rename's intent was future-proofing, prefer expect(options.length).toBeGreaterThanOrEqual(7) or assert presence of specific languages. Minor.
• Native Russian wording review is out of scope for a code-quality pass; the author invited refinement during review.

Process flag for @Finesssee (not #248's fault): the PR body reports pnpm run tauri:build:debug currently fails on two pre-existing TS errors (ProviderUsageSnapshot.localUsage in MenuCardDetails.tsx, a null assignment in providerGridUtils.test.ts) in files this PR doesn't touch. The hosted PR check runs pnpm run build; if those errors are real on main, the build step will fail regardless of this PR. Worth confirming whether main is currently build-broken independently.

[Finesssee]

Thanks for the quick turnaround — both review items are addressed: the language-picker test now uses toBeGreaterThanOrEqual(7), and the two build-breaking TS errors are patched.

Heads-up on overlap: main already carries the same two one-line TS fixes since #250 merged (byte-identical patches — MenuCardDetails localUsage type and the providerGridUtils fixture). A rebase onto current main turns your b106dbb hunks into no-ops and unblocks the hosted build step (main is green again: pnpm run build passes, plus the previously flaky cost-scan tests are now deterministic).

Whenever you're ready: mark the PR ready-for-review + rebase onto main, and the hosted check should go green — happy to merge from there. The localization work itself is approved as-is.

[Finesssee]

Approved — thermo-nuclear review passed, both nits addressed in b106dbb. Merging.

[Finesssee]

Merged 🎉 Thank you @serezha93 — first Russian UI for Win-CodexBar. 712-key catalog, aliases, bridge wiring and tests all in one clean PR, and you handled the review fixes quickly. Ships in the next release; native wording refinements are welcome as follow-up PRs.