refactor(documents): drop duplicate sender/receiver in list rows

The desktop document-list row showed sender/receiver twice — once
side-by-side in the middle column and again stacked in the right
column. Stack the middle-column block vertically (the side-by-side
grid wasted horizontal space and competed with the larger thumbnail)
and remove the now-redundant copy from the right column.

The middle-column block keeps the search-match highlighting, which the
right-column copy never had.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/lib/components/DocumentRow.svelte.spec.ts

@@ -117,6 +117,30 @@ describe('DocumentRow – sender', () => {
 		const unknownElements = page.getByText('Unbekannt');
 		await expect.element(unknownElements.first()).toBeInTheDocument();
 	});
+
+	it('renders the sender display name only once across the row', async () => {
+		const item = makeItem({
+			document: {
+				...makeItem().document,
+				sender: { id: 's1', displayName: 'Großmutter Maria' }
+			}
+		});
+		render(DocumentRow, { item });
+		const matches = await page.getByText('Großmutter Maria').all();
+		expect(matches.length).toBe(1);
+	});
+
+	it('renders each receiver display name only once across the row', async () => {
+		const item = makeItem({
+			document: {
+				...makeItem().document,
+				receivers: [{ id: 'r1', displayName: 'Onkel Karl' }]
+			}
+		});
+		render(DocumentRow, { item });
+		const matches = await page.getByText('Onkel Karl').all();
+		expect(matches.length).toBe(1);
+	});
 });
 
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