Fix setupExe metadata + improve PKSFX detection

- Added 'sfx' and 'makesfx' to SKIP_EXE_NAMES
- Increased self-extractor detection buffer to 32KB
- Fixed false-positive risk: PK signatures only checked after offset 0x40
  using proper signature comparison (not sequential byte matching)
- Fixed setupExe metadata: only set when setup bundle was actually created,
  preventing phantom Setup button when setup exe is Windows

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

@@ -106,11 +106,13 @@ public class UploadResource {
             // 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".
+            boolean hasSetupBundle = false;
             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);
+                    hasSetupBundle = true;
                 }
             }
 
@@ -118,7 +120,9 @@ public class UploadResource {
             Game game = new Game(gameId, title);
             game.setBundleFile(bundleFile);
             game.setPlatform(platform);
-            game.setSetupExe(setupExe != null ? extractDir.relativize(Path.of(setupExe)).toString() : null);
+            if (hasSetupBundle) {
+                game.setSetupExe(extractDir.relativize(Path.of(setupExe)).toString());
+            }
             game.setReady(true);
             svc.save(game);
 
@@ -291,25 +295,27 @@ public class UploadResource {
      */
     static boolean isLikelySelfExtractor(Path exePath) {
         try (var fis = Files.newInputStream(exePath)) {
-            byte[] buf = new byte[4096];
+            byte[] buf = new byte[32768]; // 32KB to cover most PKSFX stubs
             int read = fis.readNBytes(buf, 0, buf.length);
             if (read < 0x40) return false;
             // Must start with MZ
             if (buf[0] != 0x4D || buf[1] != 0x5A) return false;
-            // Scan the MS-DOS stub area (after the header) for PKWARE signatures
-            // PKSFX/PKZIP stubs contain strings like "PKZIP", "PK", "PKSFX"
-            // in the first few KB of the executable
+            // Scan for PKWARE text signatures in the MS-DOS stub area
             String content = new String(buf, 0, read, java.nio.charset.StandardCharsets.ISO_8859_1);
             if (content.contains("PKZIP") || content.contains("PKSFX"))
                 return true;
-            // Check for the typical PKWARE "PK\x03\x04" local file header signature
-            // which appears in append-to-exe style self-extractors
-            for (int i = 0; i < read - 4; i++) {
-                if (buf[i] == 0x50 && buf[i+1] == 0x4B && buf[i+2] == 0x03 && buf[i+3] == 0x04)
-                    return true;
-                if (buf[i] == 0x50 && buf[i+1] == 0x4B && buf[i+2] == 0x05 && buf[i+3] == 0x06)
+            // Check for PKWARE zip signatures in appended zip data.
+            // Only check at reasonable offsets (past the MZ header + stub)
+            // to avoid false positives on code bytes that happen to be 0x50,0x4B.
+            for (int i = 0x40; i < read - 4; i++) {
+                int p = buf[i] & 0xFF;
+                // PK\x03\x04 = local file header, PK\x01\x02 = central dir
+                if (p == 0x50 && (buf[i+1] & 0xFF) == 0x4B) {
+                    int sig = (buf[i+2] & 0xFF) | ((buf[i+3] & 0xFF) << 8);
+                    if (sig == 0x0403 || sig == 0x0201 || sig == 0x0605)
                         return true;
                 }
+            }
             return false;
         } catch (IOException e) {
             return false;
@@ -379,7 +385,7 @@ public class UploadResource {
         "debug",                                   // Debugger
         "uninst", "uninstall", "uninstaller",       // Uninstallers
         // Compression / archive tools (self-extractors)
-        "pksfx", "pkzip", "pkunzip",               // PKWARE
+        "pksfx", "pkzip", "pkunzip", "sfx", "makesfx", // PKWARE
         "unzip", "zip", "zip2exe",                 // Info-ZIP
         "arj", "arj32",                            // ARJ
         "lha", "lha32", "lzh",                     // LHA/LHarc