OZG-1063 change aria-labels to german

...ion/src/lib/header-container/header/header.component.html

...page-container/postfach-page/postfach-page.component.html

...src/lib/ui/expansion-panel/expansion-panel.component.html

...libs/ui/src/lib/ui/file-upload/file-upload.component.html

...tton-with-spinner/icon-button-with-spinner.component.html

...on-container/user-profile-button-container.component.html

...ib/vorgang-detail-page/vorgang-detail-page.component.html

...ch-container/vorgang-search/vorgang-search.component.html

...orlage-in-vorgang/wiedervorlage-in-vorgang.component.html

...ction-buttons/wiedervorlage-action-buttons.component.html