feat(notification): add dismiss-notification and mark-all-read form actions to aktivitaeten

Adds two SvelteKit form actions to /aktivitaeten/+page.server.ts so the
notification bell can POST there instead of calling the backend directly
from the browser.

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

frontend/src/routes/aktivitaeten/page.server.spec.ts

@@ -1,8 +1,10 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest';
-import { load } from './+page.server';
+import { load, actions } from './+page.server';
 
 const mockApi = {
-	GET: vi.fn()
+	GET: vi.fn(),
+	PATCH: vi.fn(),
+	POST: vi.fn()
 };
 
 vi.mock('$lib/shared/api.server', () => ({
@@ -173,3 +175,77 @@ describe('aktivitaeten/load — kinds param per filter', () => {
 		expect(call[1].params.query.kinds).toHaveLength(2);
 	});
 });
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function makeActionEvent(formData: FormData): any {
+	return {
+		request: new Request('http://localhost/aktivitaeten', { method: 'POST', body: formData }),
+		fetch
+	};
+}
+
+describe('aktivitaeten/actions — dismiss-notification', () => {
+	it('calls PATCH /api/notifications/{id}/read with the form-supplied notificationId', async () => {
+		mockApi.PATCH.mockResolvedValue({ response: { ok: true }, data: {} });
+		const fd = new FormData();
+		fd.set('notificationId', 'n-abc');
+
+		await actions['dismiss-notification'](makeActionEvent(fd));
+
+		expect(mockApi.PATCH).toHaveBeenCalledWith('/api/notifications/{id}/read', {
+			params: { path: { id: 'n-abc' } }
+		});
+	});
+
+	it('returns { success: true } when the API responds ok', async () => {
+		mockApi.PATCH.mockResolvedValue({ response: { ok: true }, data: {} });
+		const fd = new FormData();
+		fd.set('notificationId', 'n-abc');
+
+		const result = await actions['dismiss-notification'](makeActionEvent(fd));
+
+		expect(result).toEqual({ success: true });
+	});
+
+	it('returns fail(status, { error }) when the API responds non-ok', async () => {
+		mockApi.PATCH.mockResolvedValue({
+			response: { ok: false, status: 403 },
+			error: { code: 'NOTIFICATION_NOT_FOUND' }
+		});
+		const fd = new FormData();
+		fd.set('notificationId', 'n-abc');
+
+		const result = await actions['dismiss-notification'](makeActionEvent(fd));
+
+		expect(result).toMatchObject({ status: 403 });
+	});
+});
+
+describe('aktivitaeten/actions — mark-all-read', () => {
+	it('calls POST /api/notifications/read-all', async () => {
+		mockApi.POST.mockResolvedValue({ response: { ok: true }, data: null });
+
+		await actions['mark-all-read'](makeActionEvent(new FormData()));
+
+		expect(mockApi.POST).toHaveBeenCalledWith('/api/notifications/read-all');
+	});
+
+	it('returns { success: true } when the API responds ok', async () => {
+		mockApi.POST.mockResolvedValue({ response: { ok: true }, data: null });
+
+		const result = await actions['mark-all-read'](makeActionEvent(new FormData()));
+
+		expect(result).toEqual({ success: true });
+	});
+
+	it('returns fail(status, { error }) when the API responds non-ok', async () => {
+		mockApi.POST.mockResolvedValue({
+			response: { ok: false, status: 500 },
+			error: { code: 'INTERNAL_ERROR' }
+		});
+
+		const result = await actions['mark-all-read'](makeActionEvent(new FormData()));
+
+		expect(result).toMatchObject({ status: 500 });
+	});
+});