Upgrade Express to v5 +Canvas v3 + code cleanup

package.json

@@ -34,7 +34,7 @@
     "color": "4.2.3",
     "commander": "12.1.0",
     "cors": "2.8.5",
-    "express": "4.19.2",
+    "express": "5.0.1",
     "handlebars": "4.7.8",
     "http-shutdown": "1.2.2",
     "morgan": "1.10.0",

src/main.js

@@ -1,6 +1,12 @@
 #!/usr/bin/env node
 
 'use strict';
+import os from 'os';
+
+const envSize = parseInt(process.env.UV_THREADPOOL_SIZE, 10);
+process.env.UV_THREADPOOL_SIZE = Math.ceil(
+  Math.max(4, isNaN(envSize) ? os.cpus().length * 1.5 : envSize),
+);
 
 import fs from 'node:fs';
 import fsp from 'node:fs/promises';