refactor: move lib-root files to lib/shared/ and finalize domain structure

- Move api.server.ts, errors.ts, types.ts, utils.ts, relativeTime.ts to lib/shared/
- Move person relationship components to lib/person/relationship/
- Move Stammbaum components to lib/person/genealogy/
- Move HelpPopover to lib/shared/primitives/
- Update all import paths across routes, specs, and lib files
- Update vi.mock() paths in server-project test files
- Remove now-empty legacy directories (components/, hooks/, server/, etc.)
- Update vite.config.ts coverage include paths for new structure
- Update frontend/CLAUDE.md to reflect domain-based lib/ layout

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

frontend/src/routes/admin/users/layout.server.spec.ts

@@ -1,9 +1,9 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 import { load } from './+layout.server';
 
-vi.mock('$lib/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
 
-import { createApiClient } from '$lib/api.server';
+import { createApiClient } from '$lib/shared/api.server';
 
 function mockApi(users: unknown[]) {
 	vi.mocked(createApiClient).mockReturnValue({