feat(videocall): add videocall_sdk package wrapping Juphoon jc_sdk

Full wrapper around jc_sdk v2.16.5 with clean architecture:
- 7 services covering 100% of jc_sdk public API (Client, Call, Device, Channel, Push, Net, Log)
- Constructor injection with GetIt DI module (follows sca_treezor pattern)
- VideocallSdkManager orchestrator for init/destroy lifecycle
- VideocallSdkConfig abstract for environment-specific AppKey
- Stream-based callbacks for reactive UI consumption
- Riverpod providers (service + stream) for feature layer
- AppKey configured per environment via dart-define-from-file
- Integrated in init_app.dart alongside scaTreezorModule

apps/mobile_app/pubspec.yaml

@@ -91,6 +91,8 @@ dependencies:
     path: ../../packages/sca_treezor
   payments:
     path: ../../packages/payments
+  videocall_sdk:
+    path: ../../packages/videocall_sdk
   #dependencies go here
   cupertino_icons: ^1.0.8
   flutter_svg: ^2.2.2