fix: upgrade mailing from 0.8.19 to 0.9.12

Snyk has created this PR to upgrade mailing from 0.8.19 to 0.9.12.

See this package in npm:
https://www.npmjs.com/package/mailing

See this project in Snyk:
https://app.snyk.io/org/q1bluequantumblockchainlabs.onmicrosoft.com/project/bb8c7f19-7666-4860-a766-b70692ba22ed?utm_source=github&utm_medium=referral&page=upgrade-pr

packages/email-server/package.json

@@ -46,7 +46,7 @@
     "fastify-plugin": "^4.3.0",
     "html-minifier": "^4.0.0",
     "luxon": "^3.1.0",
-    "mailing": "^0.8.12",
+    "mailing": "^0.9.12",
     "mailing-core": "^0.8.12",
     "mjml": "^4.13.0",
     "mjml-react": "^2.0.8",