test(dashboard): add partial-failure resilience test + fix i18n Dok. key

- page.server.spec.ts: new test verifies topPersons=[] when that fetch
  rejects, rest of reader data still loads — addresses @Sara concern
- ReaderPersonChips: replaces hardcoded "Dok." with
  dashboard_reader_doc_count_suffix Paraglide key (de/en/es)
  — addresses @Felix suggestion

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

frontend/src/lib/shared/dashboard/ReaderPersonChips.svelte

@@ -45,7 +45,9 @@ const { persons }: Props = $props();
 				</span>
 				<span class="flex min-w-0 flex-col">
 					<span class="text-ink-1 truncate font-serif text-sm">{p.displayName ?? p.lastName}</span>
-					<span class="font-sans text-xs text-ink-3">{p.documentCount ?? 0} Dok.</span>
+					<span class="font-sans text-xs text-ink-3"
+						>{p.documentCount ?? 0} {m.dashboard_reader_doc_count_suffix()}</span
+					>
 				</span>
 			</a>
 		{/each}