Add dialog showing diff of changes to save

Add a save dialog at the bottom of the screen that is present whenever
there are unsaved changes.  This dialog provides a diff between the
client and server state so that the user can easily confirm the changes
they are about to make are the correct changes before applying them to
the server.

components/DiffEntry.vue

@@ -0,0 +1,48 @@
+<template>
+	<div
+		v-if="entries.length"
+		class="diffEntry"
+	>
+		<div class="title">
+			{{ title }}:
+		</div>
+		<div
+			v-for="[type, text], index in entries"
+			:key="index"
+			:class="type"
+		>
+			{{ text }}
+		</div>
+	</div>
+</template>
+
+<script lang="ts" setup>
+defineProps<{
+	title: string,
+	entries: (["removed" | "added", string][]);
+}>();
+</script>
+
+<style scoped>
+.diffEntry {
+	display: grid;
+	grid-template-columns: 5rem 1fr;
+	column-gap: 1rem;
+}
+.removed {
+	grid-column: 2 / 2;
+	color: color-mix(in srgb, CanvasText, red 40%);
+}
+.removed::before {
+	content: "- ";
+	font-family: monospace;
+}
+.added {
+	grid-column: 2 / 2;
+	color: color-mix(in srgb, CanvasText, green 40%);
+}
+.added::before {
+	content: "+ ";
+	font-family: monospace;
+}
+</style>