Check setup EXE's own platform before creating setup bundle

Previously only checked the main game's platform. Fallout's SETUP.EXE
is a Windows executable even though FALLOUT.EXE is DOS — creating a
.setup.jsdos bundle for it would show 'This program cannot run in DOS mode'.
Now detects the setup EXE's own header and skips if it targets Windows.

src/main/java/com/dostalgia/UploadResource.java

@@ -103,11 +103,15 @@ public class UploadResource {
             // Detect platform (DOS vs Windows) by reading the main EXE header
             String platform = detectPlatform(Path.of(mainExe));
 
-            // Create setup bundle only if the game is a DOS executable
-            // (Windows setup bundles are useless — they need Windows to run)
-            if (setupExe != null && !"windows".equals(platform)) {
-                Path setupBundlePath = svc.getGamesDir().resolve(gameId + ".setup.jsdos");
-                createBundle(extractDir, setupExe, setupBundlePath);
+            // Create setup bundle only if the setup executable is itself DOS-compatible.
+            // Some games (e.g. Fallout) ship a Windows SETUP.EXE even though the main
+            // game is DOS — that setup would fail with "This program cannot run in DOS mode".
+            if (setupExe != null) {
+                String setupPlatform = detectPlatform(Path.of(setupExe));
+                if (!"windows".equals(setupPlatform)) {
+                    Path setupBundlePath = svc.getGamesDir().resolve(gameId + ".setup.jsdos");
+                    createBundle(extractDir, setupExe, setupBundlePath);
+                }
             }
 
             // Save metadata