OZG-635 styling search-field part 1

...gation/src/lib/header-container/header/_header.theme.scss

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

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

...-search-container/vorgang-search-container.component.scss

...ng-search-container/vorgang-search-container.component.ts

...ib/vorgang-search-container/vorgang-search.formservice.ts