feat: add Node.js/Express API with real data from Desk CRM

- ✅ API completa em /api com TypeScript
- ✅ Google Calendar integration (pessoal + profissional)
- ✅ Queries diretas à BD: tasks, leads, projectos, billing, pipeline
- ✅ Endpoints: /api/dashboard, /api/monitor, /api/health
- ✅ Vite proxy configurado (/api → localhost:3001)
- ✅ App.tsx usa /api/dashboard (não mais dados mock)
- ✅ Migração completa do PHP (index.php + monitor.php)
- ✅ CHANGELOG.md criado para tracking
- ✅ Scripts npm: dev (paralelo), dev:api, dev:ui, start

Dependencies:
- express, cors, mysql2, googleapis
- concurrently, tsx (dev)

Breaking: PHP backend será descontinuado
See: CHANGELOG.md, api/README.md

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,12 @@
+# Database Configuration
+DB_HOST=localhost
+DB_USER=ealmeida_desk24
+DB_PASS=your_password_here
+DB_NAME=ealmeida_desk24
+
+# API Configuration
+API_PORT=3001
+FRONTEND_URL=http://localhost:5173
+
+# Production URLs
+# FRONTEND_URL=https://dash.descomplicar.pt