Add automatic cover art fetching from LibRetro thumbnails

Downloads box art from libretro-thumbnails GitHub repos for all
supported consoles (PS1, NES, SNES, N64, Genesis, PS2). Art is
fetched in the background on first scan and cached locally. Also
fixes multi-track .bin files showing as separate game entries.

gradle/libs.versions.toml

@@ -14,6 +14,7 @@ lifecycle = "2.9.0"
 coroutines = "1.10.2"
 windowSizeClass = "1.3.2"
 datastorePrefs = "1.1.4"
+coil = "2.7.0"
 
 [libraries]
 androidx-core-ktx = { group = "androidx.core", name = "core-ktx", version.ref = "coreKtx" }
@@ -47,6 +48,9 @@ coroutines-android = { group = "org.jetbrains.kotlinx", name = "kotlinx-coroutin
 # DataStore
 datastore-prefs = { group = "androidx.datastore", name = "datastore-preferences", version.ref = "datastorePrefs" }
 
+# Coil (image loading)
+coil-compose = { group = "io.coil-kt", name = "coil-compose", version.ref = "coil" }
+
 [plugins]
 android-application = { id = "com.android.application", version.ref = "agp" }
 kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }