feat: refactor and optimize frontend with Next.js App Router, TypeScript, and Tailwind CSS

- Complete refactoring of old frontend into Next.js App Router workspace
- Redesigned sidebar collapsing animation with absolute toggle positioning
- Resolved visual canvas bleed transitions between light/dark themes
- Added custom dark theme variant for toggle switch buttons
- Implemented full localization across Indonesian, English, Spanish, Japanese, and Chinese
- Synchronized HTML document themes to apply dark mode styles to portals/overlays

frontend/_not-found/__next._tree.txt

@@ -0,0 +1,2 @@
+:HL["/_next/static/chunks/0~n~ndg8g34g9.css","style"]
+0:{"tree":{"name":"","param":null,"prefetchHints":16,"slots":{"children":{"name":"/_not-found","param":null,"prefetchHints":0,"slots":{"children":{"name":"__PAGE__","param":null,"prefetchHints":0,"slots":null}}}}},"staleTime":300,"buildId":"ncF6Dp_0OCMhTp1KUVnS4"}