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/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>