Replace all user-visible hardcoded Chinese strings in Vue/TS source files
with proper i18n function calls and add corresponding translation keys
to all 4 locale files (zh-CN, en-US, ko-KR, ru-RU).
Changes:
- Replace 80+ hardcoded Chinese strings across 30+ source files
- Add ~450 new translation keys per locale file
- Cover components, views, utils, hooks, and API modules
- Remove Chinese fallback patterns (|| '中文') from existing t() calls
- Add mermaid toolbar and ollama date format translations
Intentionally preserved (backend API values / backward compatibility):
- FAQ CSV column headers and parsing constants
- RelevanceLevel type and Record key mappings
- Graph database engine status comparison ('未启用')
- Language name labels ('简体中文')
ochan.kwon
db7cef5f17