feat: add Turkish (tr) localization support

[MaximusPrime77]

Summary

This PR adds Turkish language ( r) support to OpenWhispr's UI, making it accessible to Turkish-speaking users.

Changes

• src/locales/tr/translation.json — New: Turkish translations for all 2000+ UI strings
• src/locales/tr/prompts.json — New: Turkish versions of the AI cleanup and agent prompt templates
• src/i18n.ts — Added r to SUPPORTED_UI_LANGUAGES and i18next resources
• src/helpers/i18nMain.js — Added r to the Electron main process i18n setup
• src/locales/translations.ts — Registered Turkish translation file
• src/locales/prompts.ts — Registered Turkish prompts file
• src/components/SettingsPage.tsx — Added Türkçe 🇹🇷 option to the UI language selector

Testing

• Passed
  pm run i18n:check\ (all keys and placeholders consistent with English base)
• Turkish is fully selectable from the Interface Language dropdown in Settings