fix: recursive WAD detection + write BOTH DEFAULT.CFG and DOOM2.CFG

Previous injectDoomConfig used Files.list() which only checks the
top-level directory — if the WAD was in a subdirectory, detection
failed silently and no config was written. Switched to Files.walk()
for recursive search.

Also:
- Write BOTH DEFAULT.CFG AND DOOM2.CFG (Doom II reads DOOM2.CFG
  first as game-specific config, falling back to DEFAULT.CFG)
- Always overwrite (don't skip if file exists — the ZIP might
  contain a stock DEFAULT.CFG with arrow-key defaults)

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

@@ -340,26 +340,27 @@ public class UploadResource {
 
     /**
      * Detect Doom-engine games and inject a DEFAULT.CFG with WASD controls.
-     * Checks for DOOM.WAD or DOOM2.WAD in the source, then writes the
-     * config to the destination if it doesn't already have one.
+     * Searches recursively for DOOM.WAD / DOOM2.WAD in source, then writes
+     * config files to the destination root (where the game will look for them).
      */
     private void injectDoomConfig(Path srcDir, Path dstDir) throws IOException {
         boolean hasDoom = false;
-        try (var stream = Files.list(srcDir)) {
-            for (Path f : (Iterable<Path>) stream::iterator) {
-                String name = f.getFileName().toString().toUpperCase();
-                if (name.equals("DOOM.WAD") || name.equals("DOOM2.WAD")) {
-                    hasDoom = true;
-                    break;
-                }
-            }
+        try (var walk = Files.walk(srcDir)) {
+            hasDoom = walk.anyMatch(p -> {
+                String name = p.getFileName().toString().toUpperCase();
+                return name.equals("DOOM.WAD") || name.equals("DOOM2.WAD");
+            });
         }
-        if (!hasDoom) return;
-        // Don't overwrite an existing config
-        Path cfg = dstDir.resolve("DEFAULT.CFG");
-        if (Files.exists(cfg)) return;
-        Files.write(cfg, buildDoomDefaultCfg());
-        LOG.info("Doom detected — injected DEFAULT.CFG with WASD controls");
+        if (!hasDoom) {
+            LOG.info("No Doom WAD found in upload");
+            return;
+        }
+        LOG.info("Doom detected — injecting WASD config");
+        byte[] cfg = buildDoomDefaultCfg();
+        Files.write(dstDir.resolve("DEFAULT.CFG"), cfg);
+        // Doom II also reads DOOM2.CFG (game-specific, takes priority over DEFAULT)
+        Files.write(dstDir.resolve("DOOM2.CFG"), cfg);
+        LOG.info("Injected DEFAULT.CFG + DOOM2.CFG with WASD controls");
     }
 
     /**