Update app.py

app.py

@@ -67,7 +67,7 @@ def install_java21_local():
 # DOWNLOAD PAPER
 # ========================
 def download_paper():
-    jar_path = os.path.join(BASE_DIR, "paper.jar")
+    jar_path = os.path.join(BASE_DIR, "server.jar")
     if os.path.exists(jar_path):
         return
 
@@ -218,7 +218,7 @@ def start_server():
             "-Xms512M",
             "-Xmx1G",
             "-jar",
-            "paper.jar",
+            "server.jar",
             "--nogui"
         ],
         cwd=BASE_DIR,