Migrate the display store to Pinia

src/components/DropdownContent.vue

src/components/Element/ChildElement.vue

src/components/Element/Metadata/Metadata.vue

src/components/Element/Transcription/Token.vue

src/components/HeaderActions.vue

src/components/Image/ElementImage.vue

src/components/Image/ImageLayer.vue

src/components/Navigation/ChildrenTree/ChildrenTree.vue

src/components/Navigation/ElementInLine.vue

src/components/Navigation/ElementList.vue

src/components/Navigation/ElementNavigation.vue

src/components/Navigation/ElementThumbnail.vue

src/store/display.js

src/store/index.js

src/store/navigation.js

src/stores/display.ts

src/stores/index.ts

src/views/App.vue

src/views/Element.vue

tests/unit/store/auth.spec.js