Fix: Fabric loader launch and Bootstrap paths

- Add Fabric support in LaunchCommandBuilder.findVersionJson()
- Fix Bootstrap to properly use bin/ directory for launcher JAR
- Fix server.py to accept both ZernMC-win-*.zip and ZernMCLauncher-*.zip
- Add debug output for version.json resolution

server/main.py

@@ -1080,7 +1080,8 @@ async def download_launcher_exe():
 @app.get("/launcher/download/zip/{filename}")
 async def download_launcher_zip(filename: str):
     """Download specific launcher ZIP archive"""
-    if ".." in filename or not filename.startswith("ZernMCLauncher-") or not filename.endswith(".zip"):
+    valid_patterns = ["ZernMCLauncher-", "ZernMC-win-"]
+    if ".." in filename or not any(filename.startswith(p) for p in valid_patterns) or not filename.endswith(".zip"):
         raise HTTPException(400, "Invalid filename")
     
     file_path = BUILDS_DIR / filename