Update: Fixes, Refactoring and API Error Handling

.eslintrc.js

.vscode/settings.json

src/App.vue

src/components.d.ts

src/components/banner/Maintenance.vue

src/components/banner/Pilot.vue

src/components/coscine/CoscineCard.vue

src/components/coscine/CoscineFormGroup.vue

src/components/coscine/CoscineHeadline.vue

src/components/coscine/CoscineModal.vue

src/components/coscine/LoadingSpinner.vue

src/components/coscine/MultiSelect.vue

src/components/elements/BreadCrumbs.vue

src/components/elements/LoadingIndicator.vue

src/components/elements/Navbar.vue

src/components/elements/SidebarMenu.vue

src/components/toasts/ExpiryToast.vue

src/components/toasts/NotificationToast.vue

src/i18n/de.ts

src/i18n/en.ts