Add voice & video calling to any Android app FROM SCRATCH with the headless CometChat Calls SDK v5 (`com.cometchat:calls-sdk-android:5.0.4`) — no UI Kit. Kotlin: initFromSettings→login→generateToken→joinSession into a RelativeLayout, lifecycle-bound listeners, meet-style session rooms AND 1:1 ringing (Chat SDK v5 signaling + Calls SDK media), call logs, layouts, audio modes, recording, PiP, background service. Triggers: 'add calling from scratch android', 'standalone video call kotlin', 'headless calls sdk android', 'build my own call UI android', 'meeting room join by session id android', 'one-on-one ringing call without uikit android'.
