feat: supervise worker with pm2 instead of cron PID-check

Passenger only manages the Next.js app process; the worker now gets
the same crash-recovery/auto-restart via pm2, replacing the cron-driven
PID-file restart hack. Updates README deployment steps accordingly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -13,7 +13,11 @@
     "test": "jest",
     "worker": "tsx worker/index.ts",
     "worker:cleanup": "tsx worker/cron-cleanup.ts",
-    "worker:check": "tsx worker/cron-check.ts",
+    "worker:pm2:start": "pm2 start ecosystem.config.cjs",
+    "worker:pm2:stop": "pm2 stop ecosystem.config.cjs",
+    "worker:pm2:restart": "pm2 restart ecosystem.config.cjs",
+    "worker:pm2:status": "pm2 status ombrora-worker",
+    "worker:pm2:logs": "pm2 logs ombrora-worker",
     "db:migrate": "prisma migrate dev",
     "db:generate": "prisma generate"
   },
@@ -40,6 +44,7 @@
     "next": "^16.3.0",
     "next-intl": "^4.13.6",
     "next-themes": "^0.4.6",
+    "pm2": "^7.0.3",
     "prisma": "^7.9.1",
     "react": "^19.2.8",
     "react-dom": "^19.2.8"