chore(db): back up email templates before redesign

Store the original template subjects and bodies as restore scripts so the redesigned notifications can be reverted against DD_ECM if needed.

EnvelopeGenerator.Server/EmailTemplateBackups/DocumentAccessCodeReceived_original.sql

@@ -0,0 +1,17 @@
+-- Original email template: DocumentAccessCodeReceived (GUID 5)
+-- Backed up before redesign: 2026-10-29 16:32:15
+-- Subject: Zugriffscode für Dokument erhalten: ''[DOCUMENT_TITLE]''
+-- Restore by running this script against DD_ECM:
+UPDATE dbo.TBSIG_EMAIL_TEMPLATE
+SET BODY = N'Guten Tag [NAME_RECEIVER],<br />
+<br /><B><I>
+[NAME_SENDER]</I></B> hat Ihnen ein Dokument zum [SIGNATURE_TYPE] gesendet. <br />
+<br />
+Verwenden Sie den folgenden Zugriffscode, um das Dokument einzusehen:<br />
+<br />
+[DOCUMENT_ACCESS_CODE]<br />
+<br />
+Mit freundlichen Grüßen<br />
+<br />
+[NAME_PORTAL]'
+WHERE GUID = 5;