Switch production deployment from Docker to PM2 on Ubuntu.

Add Express gateway, ecosystem config, and one-click install with native PostgreSQL, Node, and Python venv on port 23566.

Co-authored-by: Cursor <cursoragent@cursor.com>

deploy/pm2/ecosystem.config.cjs

@@ -0,0 +1,61 @@
+const path = require('path')
+const fs = require('fs')
+
+const root = path.resolve(__dirname, '../..')
+const envPath = path.join(root, '.env')
+
+function loadEnv() {
+  const env = { NODE_ENV: 'production' }
+  if (!fs.existsSync(envPath)) return env
+  for (const line of fs.readFileSync(envPath, 'utf8').split('\n')) {
+    const trimmed = line.trim()
+    if (!trimmed || trimmed.startsWith('#')) continue
+    const idx = trimmed.indexOf('=')
+    if (idx === -1) continue
+    const key = trimmed.slice(0, idx).trim()
+    let value = trimmed.slice(idx + 1).trim()
+    if (
+      (value.startsWith('"') && value.endsWith('"')) ||
+      (value.startsWith("'") && value.endsWith("'"))
+    ) {
+      value = value.slice(1, -1)
+    }
+    env[key] = value
+  }
+  return env
+}
+
+const env = loadEnv()
+const webPort = env.WEB_PORT || '23566'
+const apiPort = env.API_PORT || '8000'
+const venvPython = path.join(root, 'backend', 'venv', 'bin', 'python')
+
+module.exports = {
+  apps: [
+    {
+      name: 'grade-api',
+      cwd: path.join(root, 'backend'),
+      script: venvPython,
+      args: `-m uvicorn app.main:app --host 127.0.0.1 --port ${apiPort}`,
+      interpreter: 'none',
+      env: {
+        ...env,
+        UPLOAD_DIR: env.UPLOAD_DIR || path.join(root, 'uploads'),
+      },
+      max_restarts: 10,
+      restart_delay: 5000,
+    },
+    {
+      name: 'grade-web',
+      cwd: path.join(root, 'deploy', 'pm2'),
+      script: 'server.js',
+      env: {
+        ...env,
+        WEB_PORT: webPort,
+        API_TARGET: env.API_TARGET || `http://127.0.0.1:${apiPort}`,
+      },
+      max_restarts: 10,
+      restart_delay: 3000,
+    },
+  ],
+}