chore: add ProGuard keep rules and MIT license

Add app/proguard-rules.pro with keep rules for Room entities/DAOs,
Media3 service and player classes, Coil BlurTransformation, and Kotlin
coroutines internals. Add MIT LICENSE file.

Made-with: Cursor

app/proguard-rules.pro

@@ -0,0 +1,38 @@
+# Room
+# Room generates implementation classes via KSP; the generated impls are accessed
+# reflectively at runtime, so the abstract database and annotated types must be kept.
+-keep class * extends androidx.room.RoomDatabase { *; }
+-keepclassmembers class * extends androidx.room.RoomDatabase {
+    abstract *;
+}
+-keep @androidx.room.Entity class * { *; }
+-keep @androidx.room.Dao interface * { *; }
+
+# Media3
+# RadioPlaybackService is declared in AndroidManifest.xml and instantiated by the system.
+-keep class xyz.cottongin.radio247.service.RadioPlaybackService { *; }
+# RadioPlayerAdapter extends SimpleBasePlayer; keep it so the player state machine
+# callbacks are not stripped.
+-keep class xyz.cottongin.radio247.service.RadioPlayerAdapter { *; }
+-keep class * extends androidx.media3.session.MediaLibraryService { *; }
+-keep class * extends androidx.media3.session.MediaSession$Callback { *; }
+-keep class * extends androidx.media3.session.MediaLibrarySession$Callback { *; }
+
+# Coil 3 - custom Transformation subclass
+-keep class xyz.cottongin.radio247.ui.util.BlurTransformation { *; }
+
+# Kotlin coroutines
+# MainDispatcherFactory and CoroutineExceptionHandler are loaded via ServiceLoader /
+# reflection; keepnames prevents renaming while still allowing shrinking.
+-keepnames class kotlinx.coroutines.internal.MainDispatcherFactory {}
+-keepnames class kotlinx.coroutines.CoroutineExceptionHandler {}
+-keepclassmembernames class kotlinx.** {
+    volatile <fields>;
+}
+
+# Suppress warnings for optional/transitive dependencies that are not present at runtime
+-dontwarn org.slf4j.**
+-dontwarn javax.annotation.**
+-dontwarn org.conscrypt.**
+-dontwarn org.bouncycastle.**
+-dontwarn org.openjsse.**