Merge branch 'OZG-5977-multi-file-upload-nachricht' into 'main'

...-e2e/src/e2e/main-tests/postfach-mail/postfach-mail.cy.ts

...ient/libs/admin/postfach-shared/src/lib/postfach.model.ts

alfa-client/libs/binary-file/src/index.ts

...ent/libs/postfach-shared/src/lib/postfach.service.spec.ts

alfa-client/libs/postfach-shared/src/lib/postfach.service.ts

...ontainer/postfach-mail-button-container.component.spec.ts

...ton-container/postfach-mail-button-container.component.ts

.../lib/postfach-mail-form/postfach-mail-form.component.html

...b/postfach-mail-form/postfach-mail-form.component.spec.ts

...rc/lib/postfach-mail-form/postfach-mail-form.component.ts

...er/postfach-nachricht-attachment-container.component.html

...er/postfach-nachricht-attachment-container.component.scss

...postfach-nachricht-attachment-container.component.spec.ts

...iner/postfach-nachricht-attachment-container.component.ts

...mail-attachments/postfach-mail-attachments.component.html

...mail-attachments/postfach-mail-attachments.component.scss

...l-attachments/postfach-mail-attachments.component.spec.ts

...h-mail-attachments/postfach-mail-attachments.component.ts

...fach-mail-list/postfach-mail/postfach-mail.component.html

...h-mail-list/postfach-mail/postfach-mail.component.spec.ts