feat: excel import (#527)

* refactor: simplify excel import

* chore: add external deepmerge utility

* chore: create import map utilities

* chore: increase size limits on uploads

* style: small presentation tweaks

* feat: resolve times on excel import, refs #508

apps/client/src/features/modals/upload-modal/preview/PreviewColumn.module.scss

@@ -0,0 +1,22 @@
+@use "../../../../theme/_ontimeColours" as *;
+
+@mixin pad-item {
+  padding-left: 0.5rem;
+  padding-right: 1rem;
+}
+
+.previewTable {
+  display: grid;
+  grid-template-columns: auto 1fr;
+  grid-template-rows: repeat(6, auto);
+  font-size: calc(1rem - 2px);
+}
+
+.field {
+  font-weight: 200;
+  @include pad-item;
+}
+
+.value {
+  @include pad-item;
+}