Adds lifecycle log lines across the IMAP email fetch pipeline so we can
trace where a fetch run spends time or silently stops. Some IMAP inboxes
showed increasingly sparse fetch runs in production without matching
errors; existing logs did not cover job start, lock acquisition,
connection setup, or early-exit paths.
## What changed
- `Inboxes::FetchImapEmailInboxesJob`: log when a fetch job is enqueued
per inbox (temporary instrumentation).
- `Inboxes::FetchImapEmailsJob`: log job start, skip reason on early
return, lock attempt/acquisition, fetched count, processing completion,
job completion, and unexpected errors.
- `Imap::BaseFetchEmailService`: log successful IMAP connection and the
start of each header batch fetch.
All lines share the `[IMAP::FETCH_EMAIL_SERVICE]` tag for searchability.
No behavior changes.
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Co-authored-by: Sony Mathew <sony@chatwoot.com>
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