feat: Add major features - Mejoras 5-10

- Mejora 5: Órdenes de Compra integration in obra detail
- Mejora 6: Portal de Cliente with JWT auth for clients
- Mejora 7: Diagrama de Gantt for project visualization
- Mejora 8: Push Notifications with service worker
- Mejora 9: Activity Log system with templates
- Mejora 10: PWA support with offline capabilities

New features include:
- Fotos gallery with upload/delete
- Bitácora de obra with daily logs
- PDF export for reports, gastos, presupuestos
- Control de asistencia for employees
- Client portal with granular permissions
- Gantt chart with task visualization
- Push notification system
- Activity timeline component
- PWA manifest, icons, and install prompt

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

.gitignore

@@ -52,3 +52,7 @@ logs/
 
 # OS
 Thumbs.db
+
+# Uploads (user content)
+public/uploads/fotos/*
+!public/uploads/.gitkeep