fix: log terminal connect exhaustion so a dead connection isn't silent

_connect_locked logged a per-attempt WARNING but returned False on exhaustion with no
terminal line - the per-attempt lines were the only trace, so a genuinely dead IMAP
connection could read as routine retry noise with no loud terminal signal (rule-3 guard:
a swallow-to-default must carry a terminal log, and demoting/relying only on attempt lines
would leave it silent). add a terminal WARNING before the False return; keep the
per-attempt WARNING. host only (no creds) in the message.

Signed-off-by: disqualifier <dev@disqualifier.me>

src/aiomail/client.py

@@ -93,6 +93,11 @@ class IMAPClient:
                     self._mail = None
                 if attempt < self.max_retries - 1:
                     await asyncio.sleep(2 * (attempt + 1))
+        # terminal signal: all attempts are exhausted and this SWALLOWS the failure into a
+        # False return the caller branches on. without this line the per-attempt WARNINGs are
+        # the only trace, so a genuinely dead connection could look like routine noise - log
+        # the terminal exhaustion loudly so real degradation is visible, then return False.
+        log.warning("connect to %s failed after %d attempts", self.host, self.max_retries)
         return False
 
     @staticmethod