Fix: Ensure content_id consistency with Laravel Mailer for inline attachments

[ysfks]

Description

This PR addresses an issue where inline images embedded in emails sent via the laravel-sendgrid-driver do not display correctly in Gmail. The root cause is a mismatch between the Content-ID assigned to the inline attachment and the cid used in the email’s HTML.

Problem
• Laravel Mailer uses a custom cid for inline attachments generated by $message->embed() instead of the Content-ID generated by Symfony Mailer.
• The mismatch breaks the cid reference in Gmail, causing inline images to fail to render, even though they work in other email clients (e.g., Outlook).

Solution
• Update the SendgridTransport.php file to use Laravel’s attachment name as the content_id for inline attachments.
• This ensures consistency between the Content-ID and the cid reference, resolving the rendering issue in Gmail.

[kohlerdominik]

Tested and can confirm this works

[kohlerdominik]

@s-ichikawa could you have a look at that