Fix #16: SSL pinning in all 4 Flutter apps

- Created ssl_pinning.dart with SHA-256 DER hash pinning for intaleq.xyz and siromove.com
- Replaced http.post/http.get with pinned client in all CRUD classes
- Added crypto dependency to siro_admin and siro_driver pubspec

siro_driver/pubspec.yaml

@@ -45,6 +45,7 @@ dependencies:
   # Services & Hardware
   battery_plus: ^7.0.0
   connectivity_plus: ^6.1.5
+  crypto: ^3.0.3
   device_info_plus: 11.2.2
   envied: ^1.0.0
   firebase_auth: ^6.3.0