deps: update resend requirement from >=2.30.0 to >=2.30.1 in /backend

Updates the requirements on [resend](https://github.com/resendlabs/resend-python) to permit the latest version.
- [Release notes](https://github.com/resendlabs/resend-python/releases)
- [Commits](resend/resend-python@v2.30.0...v2.30.1)

---
updated-dependencies:
- dependency-name: resend
  dependency-version: 2.30.1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

backend/pyproject.toml

@@ -29,7 +29,7 @@ dependencies = [
     "croniter>=6.0.0",
     "celery-redbeat>=2.2.0",
     "stripe>=15.1.0",
-    "resend>=2.30.0",
+    "resend>=2.30.1",
     "httpx>=0.28.0",
     "posthog>=7.0.0",
 ]