feat: implement user management system

- Add role field to UserProfile (superadmin/admin/trainer)
- Add role-based permission classes
- Create UserManagementViewSet with CRUD and password change
- Add API types and components for user management
- Create users management page in settings
- Only superadmins can manage users

frontend/server.js

@@ -0,0 +1,55 @@
+const http = require('http');
+const fs = require('fs');
+const path = require('path');
+
+const PORT = 3000;
+const PUBLIC_DIR = path.join(__dirname, 'public');
+
+const server = http.createServer((req, res) => {
+  let filePath = path.join(PUBLIC_DIR, req.url === '/' ? 'index.html' : req.url);
+  
+  // Set CORS headers for PWA
+  res.setHeader('Access-Control-Allow-Origin', '*');
+  res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
+  res.setHeader('Access-Control-Allow-Headers', 'Content-Type');
+  
+  // Set cache headers for icons and manifest
+  if (req.url.includes('.png') || req.url.includes('.json') || req.url.includes('.svg')) {
+    res.setHeader('Cache-Control', 'public, max-age=31536000');
+  }
+  
+  const ext = path.extname(filePath);
+  const contentTypes = {
+    '.html': 'text/html',
+    '.js': 'text/javascript',
+    '.css': 'text/css',
+    '.json': 'application/json',
+    '.png': 'image/png',
+    '.jpg': 'image/jpeg',
+    '.svg': 'image/svg+xml',
+    '.ico': 'image/x-icon',
+    '.woff': 'font/woff',
+    '.woff2': 'font/woff2',
+  };
+  
+  const contentType = contentTypes[ext] || 'application/octet-stream';
+  
+  fs.readFile(filePath, (err, content) => {
+    if (err) {
+      if (err.code === 'ENOENT') {
+        res.writeHead(404, { 'Content-Type': 'text/html' });
+        res.end('<h1>404 Not Found</h1>');
+      } else {
+        res.writeHead(500);
+        res.end(`Server Error: ${err.code}`);
+      }
+    } else {
+      res.writeHead(200, { 'Content-Type': contentType });
+      res.end(content, 'utf-8');
+    }
+  });
+});
+
+server.listen(PORT, () => {
+  console.log(`PWA Server running at http://localhost:${PORT}`);
+});