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

app/services/imap/authentication_error.rb

@@ -0,0 +1 @@
+class Imap::AuthenticationError < StandardError; end

app/services/imap/base_fetch_email_service.rb

@@ -107,7 +107,11 @@ class Imap::BaseFetchEmailService
 
   def build_imap_client
     imap = Net::IMAP.new(channel.imap_address, port: channel.imap_port, ssl: true)
-    imap.authenticate(authentication_type, channel.imap_login, imap_password)
+    begin
+      imap.authenticate(authentication_type, channel.imap_login, imap_password)
+    rescue Net::IMAP::NoResponseError => e
+      raise Imap::AuthenticationError, e.message
+    end
     imap.select('INBOX')
     imap
   end