identity: add the shared content transitions

expandEnter/collapseExit (revealable sections), itemEnter (resolved content),
animateItemMotion (lazy-list relayout) and fadeThrough — all driven by the M3
Expressive motion scheme and honouring rememberReduceMotion. Drawn from
Calendula's motion helpers.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

identity/build.gradle.kts

@@ -36,6 +36,7 @@ dependencies {
     implementation(libs.androidx.ui)
     implementation(libs.androidx.foundation)
     implementation(libs.androidx.material3)
+    implementation(libs.androidx.animation)
     // activity-compose for PredictiveBackHandler + BackEventCompat (the back-gesture peek).
     implementation(libs.androidx.activity.compose)
 }