fix: ship nodemailer in the API image

E-mail copies of notifications need nodemailer at runtime, but the image
installs only the dependencies listed in apps/api/package.json, so the API
crashed on start with "Cannot find module 'nodemailer'" and the container
never became healthy.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/package.json

@@ -25,6 +25,7 @@
     "ioredis": "^5.11.1",
     "joi": "^18.2.9",
     "mongoose": "^8.24.4",
+    "nodemailer": "^7.0.13",
     "pg": "^8.23.1",
     "reflect-metadata": "^0.2.0",
     "rxjs": "^7.8.0",