fix(auth-service): name email recipient log field consistently

The client-branded OTP delivery log exposed its recipient under the generic to field, while related authentication logs use email. This made structured log queries inconsistent.\n\nPublish the same recipient value under email and document the operator-facing field rename.\n\nCo-authored-by: OpenAI Codex <codex@openai.com>

Author: aspiers

.changeset/email-log-recipient-field.md

@@ -0,0 +1,9 @@
+---
+'ePDS': minor
+---
+
+Email delivery logs use a consistent recipient field.
+
+**Affects:** Operators
+
+**Operators:** Update structured-log queries for `Sent client-branded OTP email` to read the recipient from `email` instead of `to`.

packages/auth-service/src/email/sender.ts

@@ -133,7 +133,7 @@ export class EmailSender {
           html: branded.html,
         })
         logger.info(
-          { to, clientId: opts.clientId },
+          { email: to, clientId: opts.clientId },
           'Sent client-branded OTP email',
         )
         return