fold2 finding 1 (2c, Medium): the connect-time missing-pin warning was gated on
`not is_reconnect`. An account whose FIRST startup connect fails (transient
IMAP/SMTP error) is brought up by the reconnect watcher with is_reconnect=True,
so it never warned while silently dropping every sender's mail.
Dedupe per address instead: a class-level _missing_pin_warned set (the watcher
builds a fresh adapter per retry, like _seen_uids_snapshot), checked after both
IMAP and SMTP probes succeed. The existing connect test now covers a failed
first connect followed by a reconnect (one warning), a second reconnect (none),
two accounts (one each) and pinned/opted-out accounts (silent).
8b66a51036