Fix playListNumber to stream-name mapping; add JavaFX ui module

- Playlist.streamForPlayListNumber maps the 1-based playListNumber to the
  actual stream entry; stream names are not sequential across discs
  (The Dark Knight: 00001/00003/00004; The Day After Tomorrow has
  duplicate 00002 names).
- CLI menu playback now resolves the correct .MPS file for every region.
- ui module: JavaFX via org.openjfx.javafxplugin + PlayerApp smoke test
  (window verified on this display).
- Validated menus + playback on 4 discs: Batman Begins (USA), Jackass
  (Australia), The Dark Knight (Europe), The Day After Tomorrow (Japan).

core/src/main/java/dev/quoije/umd/playlist/Playlist.java

@@ -27,6 +27,16 @@ public final class Playlist {
         return streams;
     }
 
+    /** Returns the stream with the given 1-based playListNumber, or null. */
+    public Stream streamForPlayListNumber(int playListNumber) {
+        for (Stream stream : streams) {
+            if (stream.playListNumber() == playListNumber) {
+                return stream;
+            }
+        }
+        return null;
+    }
+
     /** A single MPS stream (playlist item). */
     public record Stream(
             String name,