Adds a complete Korean locale (surfsense_web/messages/ko.json) with full
key parity with en.json, and wires ko into every place locales are
currently enumerated: next-intl routing config, the client-side locale
context/loader, and the two language-switcher UIs (main app + sidebar
user profile).
- Deleted the empty middleware file as it was temporarily disabled for client-side i18n implementation.
- Updated `next`, `next-intl`, and `fumadocs` packages to their latest versions.
- Cleaned up the `next.config.ts` by removing the eslint configuration.
- Enhanced `tsconfig.json` with additional paths for `fumadocs-mdx`.
- Adjusted imports in `layout.tsx` and `request.ts` for better structure and functionality.
