feat: data export — CSV export for tasks, users, activities

- Backend: GET /api/export/{tasks,users,activities}?month=YYYY-MM
- Frontend: Export panel on Reports page (CEO/CTO/Manager only)
- API: apiExportCsv helper for browser download

server/index.js

@@ -3,6 +3,7 @@ import cors from 'cors';
 import { initDB } from './db.js';
 import authRoutes from './routes/auth.js';
 import taskRoutes from './routes/tasks.js';
+import exportRoutes from './routes/export.js';
 
 const app = express();
 const PORT = process.env.PORT || 3001;
@@ -13,6 +14,7 @@ app.use(express.json());
 // Routes
 app.use('/api/auth', authRoutes);
 app.use('/api/tasks', taskRoutes);
+app.use('/api/export', exportRoutes);
 
 // Health check
 app.get('/api/health', (_req, res) => {