P6 Stream V: ImageCompression (expect/actual) + CameraPicker polish

Android: BitmapFactory + ExifInterface + JPEG quality 0.7 + 1920px downscale.
iOS: UIImage.jpegData. JVM/JS/WASM: no-op. CameraPicker uses TakePicture
ActivityResult + permission rationale.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

composeApp/build.gradle.kts

@@ -78,6 +78,9 @@ kotlin {
             // Biometric authentication (requires FragmentActivity)
             implementation("androidx.biometric:biometric:1.1.0")
             implementation("androidx.fragment:fragment-ktx:1.8.5")
+
+            // EXIF orientation reader for ImageCompression (P6 Stream V)
+            implementation("androidx.exifinterface:exifinterface:1.3.7")
         }
         iosMain.dependencies {
             implementation(libs.ktor.client.darwin)