Add Russian localization and i18n foundation

[DrMaks22]

Summary

• Add a lightweight, project-native i18n foundation for both desktop shells: Svelte/Tauri TypeScript catalogs plus native SwiftPM Localizable resources and an L10n facade.
• Add professional Russian UI coverage across high-visibility surfaces: navigation, Dashboard, Library, Discover, Trending, Snapshots, Services, Activity, Settings, Package detail, update/security/network copy, recovery flows, GitHub sign-in text, and common action/error states.
• Preserve stable contracts: Homebrew tokens, formula/cask names, brew commands and flags, route/storage keys, API names, URLs, product/provider names, and Brewfile as a format name.
• Add localized enrichment overlays for package prose: English base enrichment remains canonical, while enrichment.<locale> partial overlays replace user-facing prose and add locale-specific search_terms without translating package identifiers, similar, or technical tags.
• Make search locale-aware in both shells: Russian package summaries/use cases/search aliases and localized category names are indexed while English fallback, exact package-token search, and stable IDs continue to work.
• Add a Russian seed package-prose overlay for common packages (wget, curl, git, node, python@3.13, postgresql@14, visual-studio-code, firefox, google-chrome, vlc, docker, slack, neovim, ripgrep, openssl@3, ffmpeg, redis, kubernetes-cli).

Future Localization Path

• tools/enrich/README.md now documents the intended workflow for additional languages:
  1. Add the UI locale first (src/lib/i18n, language selector, native Localizable resources, native locale routing).
  2. Add optional package-prose overlays as native/Sources/BrewBrowserKit/Resources/enrichment.<locale>.json.
  3. Generate the matching Tauri gzip at src-tauri/data/enrichment.<locale>.json.gz with deterministic gzip settings.
  4. Add the locale bucket in Rust and Swift, category aliases, live-enrichment merge policy, and parity tests.
• Overlay rules are explicit: translate friendly_name, summary, use_cases; add searchable natural-language aliases in search_terms; do not translate similar, tags, package tokens, commands, flags, URLs, APIs, or product names.

Notes

• Native Activity job labels remain stored in their original semantic English form so RecentChanges parsing and existing tests keep working; rendered labels and notifications are localized through L10n.
• Runtime/upstream content such as raw Homebrew output, package descriptions from upstream, filesystem paths, URLs, and provider/product names remains unchanged unless wrapped by UI copy.
• Full localization of the entire Homebrew package catalog is intentionally not attempted in this PR. The new overlay schema is the maintainable path for curated or generated package-prose localization over time.

Validation

• npm run check passes: 0 errors, 0 warnings.
• npm test passes: 4 files, 49 tests.
• cargo fmt --manifest-path src-tauri/Cargo.toml --check passes.
• cargo test --manifest-path src-tauri/Cargo.toml passes: 671 passed, 6 ignored integration tests.
• cd native && swift build passes.
• cd native && swift test passes: 173 tests.
• git diff --check passes.
• TypeScript locale parity passes: 833 English keys / 833 Russian keys.
• Native .strings parity passes for both SwiftPM targets: 830 English keys / 830 Russian keys, no missing/extra Russian keys.
• Native .xcstrings coverage passes for both SwiftPM targets: 830 keys, no missing Russian localizations and no needs_review Russian entries.
• Russian enrichment overlay parity passes: readable native JSON and embedded Tauri gzip are semantically identical.
• ru-localization docs structure check passes for tools/enrich/README.md.
• ru-localization quality lint passes for enrichment.ru.json with 0 findings. The broader TS/native string-file lint still reports known false positives because it treats English source keys (for example "Open Settings") as visible Russian text; remaining items were manually reviewed.
• Source plural audit reports heuristic findings in native count/helper/parser code; reviewed manually. Russian-visible count strings route through ruPlural, and English Activity labels remain stable internal event identifiers with localized render output.

Visual QA Limitations

• Browser smoke and local builds cannot fully exercise signed Tauri/macOS runtime-only flows such as live Homebrew IPC, GitHub device flow, permission prompts, and package data that depends on the user's installed Homebrew state. Build/test coverage passes for both shells; release QA should still launch the packaged Russian Tauri and native apps and review those runtime-only flows.