fix(#145): deep-link notifications; show createdAt in recent docs

- Notification widget builds full link with ?commentId= and
  &annotationId= params, matching the bell notification behaviour
- Recent docs widget shows createdAt (upload date) instead of
  documentDate (the date on the original document)

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

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

@@ -9,12 +9,12 @@ afterEach(cleanup);
 type Document = {
 	id: string;
 	title: string;
-	documentDate?: string;
+	createdAt?: string;
 	sender?: { id: string; firstName: string; lastName: string };
 };
 
-function makeDoc(id: string, title: string, date?: string): Document {
-	return { id, title, documentDate: date };
+function makeDoc(id: string, title: string, createdAt?: string): Document {
+	return { id, title, createdAt };
 }
 
 describe('DashboardRecentDocuments', () => {