fix: reset the edit dialog when switching books

frontend/src/lib/components/forms/edit-book/edit-book.svelte

@@ -9,8 +9,17 @@
 	let { book, open = $bindable() }: { book?: Book; open: boolean } = $props();
 </script>
 
+<!--
+	This dialog is mounted once, in (root)/(library)/+layout.svelte, and `book`
+	changes underneath it as different books are edited. bookToEdit is never
+	cleared, so {#if book} stays true and the tab forms never unmount — they seed
+	local state from `book` on mount, so without this key you would open Edit on a
+	second book and see the first book's authors, tags and cover, then save them
+	onto the wrong record. Keying on the id remounts the forms per book.
+-->
 <Dialog.Root bind:open>
 	{#if book}
+		{#key book.id}
 		<Dialog.Content class="sm:max-w-xl">
 			<Tabs.Root value="metadata" class="h-[500px] max-w-xl py-4 md:h-[700px]">
 				<Tabs.List class="grid w-full grid-cols-3">
@@ -35,5 +44,6 @@
 				</Tabs.Content>
 			</Tabs.Root>
 		</Dialog.Content>
+		{/key}
 	{/if}
 </Dialog.Root>