Reset platform email provider to defaults

Removes DB overrides for email provider settings. Falls back to environment variables, then defaults.

Response Body

curl -X DELETE "http://localhost:3001/api/v1/admin/email-provider"

{
  "message": "string"
}

{
  "property1": null,
  "property2": null
}

{
  "property1": null,
  "property2": null
}

{
  "error": "string",
  "message": "string",
  "requestId": "string"
}

{
  "property1": null,
  "property2": null
}

{
  "error": "string",
  "message": "string",
  "requestId": "string"
}