refactor: move shared components to lib/shared/ sub-packages

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

frontend/src/lib/document/transcription/TranscriptionPanelHeader.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
 import { m } from '$lib/paraglide/messages.js';
 import { getLocale } from '$lib/paraglide/runtime.js';
-import HelpPopover from '$lib/components/HelpPopover.svelte';
+import HelpPopover from '$lib/shared/help/HelpPopover.svelte';
 
 type Props = {
 	mode: 'read' | 'edit';