Add i18n system with Turkish (tr) locale

[MertCan-Aydin]

Summary

• Adds a lightweight i18n system (src/i18n/) with t(), setLocale(), and addLocale() functions
• Extracts all hardcoded user-facing strings from settings, views, and query engine into src/i18n/locales/en.ts
• Adds Turkish (tr) locale as the first non-English translation
• Locale is auto-detected from window.moment.locale() on plugin load, with fallback to English

Test plan

• Build succeeds (npm run build)
• All existing tests pass (npm test)
• Settings tab displays correctly in English
• Settings tab displays correctly in Turkish when Obsidian language is set to Turkish
• Error messages and empty-result warnings render correctly in both locales