fix: call authorization_error! on IMAP auth failures (#13560)

## Notion document

https://www.notion.so/chatwoot/Email-IMAP-Issue-30aa5f274c928062aa6bddc2e5877a63?showMoveTo=true&saveParent=true

## Description

PLAIN IMAP channels (non-OAuth) were silently retrying failed
authentication every minute, forever. When credentials are
wrong/expired, Net::IMAP::NoResponseError was caught and logged but
channel.authorization_error! was never called — so the Redis error
counter never incremented, reauthorization_required? was never set, and
admins were never notified. OAuth channels already had this handled
correctly via the Reauthorizable concern.
Additionally, Net::IMAP::ResponseParseError (raised by non-RFC-compliant
IMAP servers) was falling through to the StandardError catch-all,
flooding
Estimated impact before fix: ~70–75 broken IMAP inboxes generating
~700k–750k wasted Sidekiq jobs/week.

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)

## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

config/installation_config.yml

@@ -96,6 +96,19 @@
   locked: false
 # ------- End of Account Related Config ------- #
 
+# ------- Transient Error Backoff Config ------- #
+- name: BACKOFF_MAX_INTERVAL_MINUTES
+  display_title: 'Backoff Max Interval (minutes)'
+  description: 'Maximum wait time in minutes between retry attempts before the backoff plateaus'
+  value: 5
+  locked: false
+- name: BACKOFF_MAX_INTERVAL_COUNT
+  display_title: 'Backoff Max Retry Count'
+  description: 'Number of additional retries at the maximum interval before prompting reauthorization'
+  value: 10
+  locked: false
+# ------- End of Transient Error Backoff Config ------- #
+
 # ------- Email Related Config ------- #
 - name: MAILER_INBOUND_EMAIL_DOMAIN
   display_title: 'Inbound Email Domain'