components: add OptionalFormSection (revealable form section)

The shared wrapper for optional edit-form fields behind a "More fields" toggle:
AnimatedVisibility with the family's expand+fade motion over a full-width Column.
Adds the first intra-kit dependency (components -> identity) for the shared
transitions.

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

components/build.gradle.kts

@@ -33,6 +33,10 @@ kotlin {
 }
 
 dependencies {
+    // identity supplies the shared motion (expandEnter/collapseExit) that the
+    // revealable components animate with.
+    implementation(project(":identity"))
+
     implementation(platform(libs.androidx.compose.bom))
     implementation(libs.androidx.ui)
     implementation(libs.androidx.foundation)