fix: validate support_email format and handle parse errors in mailer (#13958)

## Description

ConversationReplyMailer#parse_email calls
Mail::Address.new(email_string).address without error handling. When an
account's support_email contains a non-email string (e.g., "Smith
Smith"), the mail gem raises Mail::Field::IncompleteParseError, crashing
conversation transcript emails.

This has caused 1,056 errors on Sentry (EXTERNAL-CHATINC-JX) since Feb
25, all from a single account that has a name stored in the
support_email field instead of a valid email address.

Closes
https://linear.app/chatwoot/issue/CW-6687/mailfieldincompleteparseerror-mailaddresslist-can-not-parse-orsmith

## Type of change

Please delete options that are not relevant.

- [ ] 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

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Vishnu Narayanan <iamwishnu@gmail.com>

app/builders/email/base_builder.rb

@@ -1,4 +1,6 @@
 class Email::BaseBuilder
+  include EmailAddressParseable
+
   pattr_initialize [:inbox!]
 
   private
@@ -47,8 +49,4 @@ class Email::BaseBuilder
     # can save it in the format "Name <email@domain.com>"
     parse_email(account.support_email)
   end
-
-  def parse_email(email_string)
-    Mail::Address.new(email_string).address
-  end
 end