fix(tests): fix type errors in spec files after adding user to App.PageData

Add user: undefined to baseData in conversations and documents/new specs.
Change null to undefined for filePath/transcription in makeDoc fixture.
Add form: null to render calls missing it.
Fix birthYear conversion from string to number in persons/[id] server action.

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

frontend/src/routes/conversations/page.svelte.spec.ts

@@ -10,6 +10,7 @@ afterEach(cleanup);
 // ─── Test data ────────────────────────────────────────────────────────────────
 
 const baseData = {
+	user: undefined,
 	canWrite: true,
 	documents: [],
 	initialValues: { senderName: '', receiverName: '' },
@@ -31,8 +32,8 @@ const makeDoc = (overrides: Record<string, unknown> = {}) => ({
 	sender: { id: 'p1', firstName: 'Hans', lastName: 'Müller' },
 	receivers: [{ id: 'p2', firstName: 'Anna', lastName: 'Schmidt' }],
 	tags: [],
-	transcription: null,
-	filePath: null,
+	transcription: undefined,
+	filePath: undefined,
 	createdAt: '1923-04-12T00:00:00Z',
 	updatedAt: '1923-04-12T00:00:00Z',
 	...overrides