Wrap IMAP/JMAP folder and message sync in tracing spans keyed by account
and folder, logging completion counts (fetched/oversized/skipped) so a
sync run's outcome is visible without a debugger. SMTP send attempts and
their outcome are logged with the recipient COUNT only, never addresses.
Every destructive IMAP mutation (MOVE, DELETE/UID-scoped EXPUNGE) is
logged with its UID set and the UIDVALIDITY guard's pass/fail result
BEFORE the command reaches the server, so an audit trail exists even
when the guard then refuses to act. JMAP mirrors the same pre-logging
for its Email/set move/destroy, keyed by the JMAP object id instead of
a UID (JMAP has no UIDVALIDITY-equivalent to guard).
Refs #361
James Maes