Add QR pairing (terminal QR, in-app scanner, iris://pair deep link)

app/shared/build.gradle.kts

@@ -29,6 +29,9 @@ val kcefVersion = "2025.03.23"
 val markdownVersion = "0.44.0"
 // Local cache DB (messages/channels/meta; docs/10 §10.7, docs/16).
 val sqldelightVersion = "2.3.2"
+// CameraX + ML Kit for in-app QR pairing (docs/20). Android-only.
+val cameraxVersion = "1.5.1"
+val mlKitVersion = "16.1.1"
 
 kotlin {
     android {
@@ -111,6 +114,13 @@ kotlin {
             implementation("androidx.media3:media3-ui:1.11.0")
             // SAF picker (rememberLauncherForActivityResult).
             implementation("androidx.activity:activity-compose:1.13.0")
+            // CameraX + ML Kit for QR pairing (docs/20): the scanner activity
+            // uses the camera2 CameraX backend and ML Kit's barcode model.
+            implementation("androidx.camera:camera-core:$cameraxVersion")
+            implementation("androidx.camera:camera-camera2:$cameraxVersion")
+            implementation("androidx.camera:camera-lifecycle:$cameraxVersion")
+            implementation("androidx.camera:camera-view:$cameraxVersion")
+            implementation("com.google.mlkit:barcode-scanning:$mlKitVersion")
             // M5: FCM push (inert without a Firebase project / google-services.json;
             // the ntfy listener is the fallback). The google-services plugin is
             // applied conditionally in the app module.