feat(frontend): add expandable text component for long fields

Adds ExpandableText.svelte which clamps text to 10 lines and shows a
toggle button only when the content actually overflows. Applied to the
summary and transcription fields on the document detail page.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/ExpandableText.svelte

@@ -0,0 +1,33 @@
+<script lang="ts">
+import { m } from '$lib/paraglide/messages.js';
+
+let { text, maxLines = 10 }: { text: string; maxLines?: number } = $props();
+
+let expanded = $state(false);
+let el = $state<HTMLElement | undefined>(undefined);
+let isClamped = $state(false);
+
+$effect(() => {
+	if (el && !expanded) {
+		isClamped = el.scrollHeight > el.clientHeight;
+	}
+});
+</script>
+
+<div>
+	<div
+		bind:this={el}
+		style={!expanded ? `overflow: hidden; display: -webkit-box; -webkit-box-orient: vertical; -webkit-line-clamp: ${maxLines}` : ''}
+		class="rounded border border-brand-sand bg-brand-sand/30 p-5 font-serif text-sm leading-relaxed whitespace-pre-wrap text-brand-navy"
+	>
+		{text}
+	</div>
+	{#if isClamped || expanded}
+		<button
+			onclick={() => (expanded = !expanded)}
+			class="mt-2 font-sans text-xs text-gray-400 transition hover:text-brand-navy"
+		>
+			{expanded ? m.comp_expandable_show_less() : m.comp_expandable_show_more()}
+		</button>
+	{/if}
+</div>

frontend/src/routes/documents/[id]/+page.svelte

@@ -2,6 +2,7 @@
 import { m } from '$lib/paraglide/messages.js';
 import { formatDate } from '$lib/utils/date';
 import { diffWords } from 'diff';
+import ExpandableText from '$lib/components/ExpandableText.svelte';
 
 let { data } = $props();
 
@@ -592,11 +593,7 @@ function versionLabel(v: VersionSummary, index: number): string {
 									<span class="mb-2 block font-sans text-xs text-gray-400 uppercase"
 										>{m.doc_label_summary()}</span
 									>
-									<div
-										class="rounded border border-brand-sand bg-brand-sand/30 p-5 font-serif text-sm leading-relaxed whitespace-pre-wrap text-brand-navy"
-									>
-										{doc.summary}
-									</div>
+									<ExpandableText text={doc.summary} />
 								</div>
 							{/if}
 
@@ -605,11 +602,7 @@ function versionLabel(v: VersionSummary, index: number): string {
 									<span class="mb-2 block font-sans text-xs text-gray-400 uppercase"
 										>{m.form_label_transcription()}</span
 									>
-									<div
-										class="rounded border border-brand-sand bg-brand-sand/30 p-5 font-serif text-sm leading-relaxed whitespace-pre-wrap text-brand-navy"
-									>
-										{doc.transcription}
-									</div>
+									<ExpandableText text={doc.transcription} />
 								</div>
 							{/if}
 						</div>