fix: remove Content-Length from 200 responses to avoid RESTEasy buffering

RESTEasy Reactive may buffer the entire StreamingOutput when
Content-Length is set (to verify it). For a 1.2GB .jsdos file,
this loads the whole file into heap — hitting the 128MB Xmx
limit at ~10% and stalling via GC thrashing.

Full-file responses now use chunked transfer encoding (no
Content-Length), matching the original behavior. Content-Length
is still set for 206 Partial Content responses where the HTTP
spec requires it.

src/main/java/com/dostalgia/StaticResource.java

@@ -80,12 +80,11 @@ public class StaticResource {
             return Response.serverError().build();
         }
 
-        // No Range header — serve the full file (200 OK)
+        // No Range header — serve the full file (200 OK, chunked encoding)
         if (rangeHeader == null || rangeHeader.isBlank()) {
             Response.ResponseBuilder rb = Response.ok(new FileStream(file, 0, fileSize))
                 .type(contentType)
-                .header("Accept-Ranges", "bytes")
-                .header("Content-Length", fileSize);
+                .header("Accept-Ranges", "bytes");
             if (cacheControl != null) {
                 rb.header("Cache-Control", cacheControl);
             }
@@ -131,12 +130,11 @@ public class StaticResource {
         return rb.build();
     }
 
-    /** Convenience: full-file 200 response. */
+    /** Convenience: full-file 200 response (chunked encoding, no Content-Length). */
     private Response serveFull(Path file, String contentType, long fileSize, String cacheControl) {
         Response.ResponseBuilder rb = Response.ok(new FileStream(file, 0, fileSize))
             .type(contentType)
-            .header("Accept-Ranges", "bytes")
-            .header("Content-Length", fileSize);
+            .header("Accept-Ranges", "bytes");
         if (cacheControl != null) {
             rb.header("Cache-Control", cacheControl);
         }