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/stammbaum/+page.server.ts

@@ -1,6 +1,6 @@
 import { error, redirect } from '@sveltejs/kit';
-import { createApiClient } from '$lib/api.server';
-import { getErrorMessage } from '$lib/errors';
+import { createApiClient } from '$lib/shared/api.server';
+import { getErrorMessage } from '$lib/shared/errors';
 
 export async function load({ fetch }) {
 	const api = createApiClient(fetch);

frontend/src/routes/stammbaum/+page.svelte

@@ -1,8 +1,8 @@
 <script lang="ts">
 import { m } from '$lib/paraglide/messages.js';
 import { page } from '$app/state';
-import StammbaumTree from '$lib/person/StammbaumTree.svelte';
-import StammbaumSidePanel from '$lib/person/StammbaumSidePanel.svelte';
+import StammbaumTree from '$lib/person/genealogy/StammbaumTree.svelte';
+import StammbaumSidePanel from '$lib/person/genealogy/StammbaumSidePanel.svelte';
 import type { components } from '$lib/generated/api';
 
 type PersonNodeDTO = components['schemas']['PersonNodeDTO'];