feat(i18n): add Turkish language support

[altinsupernova]

Summary

• Add full Turkish (tr) localization to Vibe Kanban
• Update UiLanguage enum in Rust backend and TypeScript types
• Register Turkish in frontend i18n config and language mappings
• Create 5 translation files (1,336 total keys) covering all namespaces

Details

All translation keys match English source files 1:1. {{variable}} placeholders are preserved. Proper Turkish characters (ç, ğ, ı, ö, ş, ü, İ) are used throughout. Technical terms (Git, PR, Kanban, MCP, etc.) are kept in English per convention.

Files changed

File	Change
crates/services/src/services/config/versions/v6.rs	Add Tr variant to UiLanguage enum
shared/types.ts	Add "TR" to UiLanguage type
frontend/src/i18n/languages.ts	Add TR mapping, endonym, and supported language entry
frontend/src/i18n/config.ts	Add Turkish imports and resource registration
frontend/src/i18n/locales/tr/common.json	395 keys — buttons, states, navigation, kanban, workspace, OAuth, shortcuts
frontend/src/i18n/locales/tr/settings.json	327 keys — appearance, editor, GitHub, Git, notifications, privacy, agents, MCP
frontend/src/i18n/locales/tr/projects.json	18 keys — project list and management
frontend/src/i18n/locales/tr/tasks.json	526 keys — tasks, attempts, Git operations, diff, preview, PR creation, scripts
frontend/src/i18n/locales/tr/organization.json	70 keys — organization CRUD, invitations, members, billing

Test plan

• Select "Türkçe" from Settings → General → Appearance → Language
• Verify all UI elements render in Turkish
• Verify no missing translation keys (no fallback to English)
• Verify {{variable}} interpolations work correctly

[Juanlucasbg]

Rebase verification — PR #2785 — rebases cleanly

Local verification:

• git rebase main — clean (no conflicts).
• Targeted compile checks pass (TS errors that surface are environmental, also reproduce on main).

This is the second Turkish language pack in the queue, alongside PR #2434 (different author, similar scope). Bundle with the other queued language packs (#3096 Portuguese, #3212 Russian, #3288 Hebrew + RTL infra, #2434 Turkish).

Action: maintainer policy decision on language packs in the sunset window. Specifically for Turkish: pick whichever of #2785 / #2434 is more complete (key coverage, translation quality) and close the other. Both rebase cleanly.

— Automated rebase-verification: confirmed clean rebase locally; one of two competing Turkish PRs.