feat: allow changing recipients when resending a mail

[shyim]

Closes #143

What

Clicking Resend mail on the mail archive detail page now opens a modal that is pre-filled with the current recipients. The recipient list can be adjusted — e.g. to fix a typo in the e-mail address, which is the most common reason a mail could not be delivered — before the mail is actually resent.

How

Backend (MailArchiveController::resend)

• The resend-mail API action accepts a new optional receiver parameter: a non-empty list of e-mail addresses, each either a plain address or in Name <mail@example.com> format (parsed via Symfony\Component\Mime\Address::create()).
• When provided, the To header of the rebuilt email is replaced before sending — works for both the EML-based and the database-based rebuild path.
• Invalid input is rejected with a 400 response (MAIL_ARCHIVE__PARAMETER_INVALID_RECEIVER).
• Without the parameter, behavior is unchanged (used by the list page quick/bulk resend actions).

Administration (detail page)

• The toolbar button now opens a sw-modal with a sw-tagged-field pre-filled with the current recipients (keeping their display names), a cancel and a confirm button.
• Confirming resends with the adjusted recipients; on validation errors the modal stays open so the address can be fixed.
• New en-GB/de-DE snippets for the modal.

Note on the help text snippet

The example address in the help text escapes the @ as {'@'}: a bare @ inside a message is parsed as vue-i18n linked message syntax and makes the message compiler throw (INVALID_LINKED_FORMAT), which prevented the modal from rendering. This was verified against the vue-i18n 9 (Shopware 6.6) and 10 (Shopware 6.7) runtimes.

Testing

Verified on a real Shopware 6.7.14 installation with the plugin installed:

• Resend with corrected address via API: original mail marked resent, new archive entry created with the corrected receiver, display name preserved, source_mail_id linked to the original mail.
• Resend with invalid address: 400 MAIL_ARCHIVE__PARAMETER_INVALID_RECEIVER.
• Resend without receiver parameter: unchanged behavior (backwards compatible).
• Full UI flow in the administration (see recording): modal opens pre-filled with Max Mustermann <max.mustermann@exmaple.com>, address corrected to max.mustermann@example.com, resend succeeds, resend history shows the new sent entry.
• phpstan level max passes against shopware/core ~6.6.0 and ~6.7.0; administration JS passes the shopware-cli prettier config; snippet key parity between en-GB and de-DE verified (CI check-snippets).

Resend modal pre-filled with current recipient

Success notification and updated resend history

resend_modal_change_recipient_flow.mp4

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