I need a clean, reliable Android-only softphone that makes crystal-clear SIP voice calls and allows users to forward an incoming call to another number or SIP URI on demand. The core flow is straightforward: register to our SIP server, place or receive a voice call, and offer a one-tap option to forward that active call. Please build it in native Android (Java or Kotlin) and feel free to rely on solid VoIP stacks such as PJSIP, Linphone SDK, or WebRTC if that accelerates development. I will supply the SIP credentials and server details for testing; you just need to expose fields in a simple settings screen so I can switch accounts when needed. Push notification handling for incoming calls via FCM is essential to keep battery usage low when the app is in the background. Deliverables • Signed release APK and installable debug build • Full Android Studio project with readable, well-commented source • Brief setup guide describing how to point the build at a different SIP server and where the call-forwarding logic lives Acceptance criteria 1. App registers to my SIP server and stays registered for at least 24 h in standby. 2. Voice call quality comparable to the native dialer on a 4G network (no audible artifacts, latency < 250 ms). 3. Active call can be forwarded to another number without dropping the original connection until forwarding completes. 4. Incoming calls ring consistently through FCM even when the app has been force-quit. If you have recently shipped a SIP or WebRTC-based dialer, I would love to see a sample or short demo video with your bid so I can confirm audio quality before we start.