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-next/copy-build.js

@@ -0,0 +1,50 @@
+const fs = require('fs');
+const path = require('path');
+
+const srcDir = path.join(__dirname, 'out');
+const destDir = path.join(__dirname, '..', 'frontend');
+
+function copyDirSync(src, dest) {
+  fs.mkdirSync(dest, { recursive: true });
+  const entries = fs.readdirSync(src, { withFileTypes: true });
+
+  for (let entry of entries) {
+    const srcPath = path.join(src, entry.name);
+    const destPath = path.join(dest, entry.name);
+
+    if (entry.isDirectory()) {
+      copyDirSync(srcPath, destPath);
+    } else {
+      fs.copyFileSync(srcPath, destPath);
+    }
+  }
+}
+
+function cleanDirSync(dir) {
+  if (!fs.existsSync(dir)) return;
+  const entries = fs.readdirSync(dir, { withFileTypes: true });
+  for (let entry of entries) {
+    if (entry.name === '.git' || entry.name === '.antigravitycli') continue;
+    const fullPath = path.join(dir, entry.name);
+    if (entry.isDirectory()) {
+      fs.rmSync(fullPath, { recursive: true, force: true });
+    } else {
+      fs.unlinkSync(fullPath);
+    }
+  }
+}
+
+try {
+  console.log('Wiping old static files in frontend/ ...');
+  cleanDirSync(destDir);
+
+  console.log('Copying static Next.js assets to frontend/ ...');
+  if (fs.existsSync(srcDir)) {
+    copyDirSync(srcDir, destDir);
+    console.log('Build output synchronization successful!');
+  } else {
+    console.error('Error: "out/" directory not found. Compile the Next.js build first.');
+  }
+} catch (err) {
+  console.error('Synchronization failed:', err);
+}