Completed the sending-identity email confirmation flow end to end, and added request-level observability to the backend.
Identity confirmation flow — built the confirmation link, landing route, and a new ConfirmIdentityPage on the frontend so users can verify a sending address from the email they receive. Fixed the confirmation link 404 — the emailed link was hitting the frontend instead of the API. Introduced an apiPrefixedBaseUrl config getter so prefixed routes build correct absolute URLs in outbound email. Request/response logging — added logging middleware, interceptor and exception filter (~210 lines) covering all API traffic, plus event and sender-queue logging.