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/models/concerns/email_address_parseable.rb

@@ -0,0 +1,15 @@
+module EmailAddressParseable
+  extend ActiveSupport::Concern
+
+  private
+
+  def parse_email(email_string)
+    Mail::Address.new(email_string).address.presence || default_sender_email_address
+  rescue Mail::Field::ParseError, Mail::Field::IncompleteParseError
+    default_sender_email_address
+  end
+
+  def default_sender_email_address
+    Mail::Address.new(ENV.fetch('MAILER_SENDER_EMAIL', 'accounts@chatwoot.com')).address
+  end
+end