feat(topbar): add expandable metadata drawer with Details toggle (#175)

- DocumentMetadataDrawer: 3-column grid (≥1024px), single-column mobile
  Shows document date, location, status, person cards, tag chips
  Person names link to /persons/{id}, tags link to filtered search
  Empty states for missing persons/tags, receiver cap with expand button
- DocumentTopBar: "Details" toggle button with animated SVG chevron
  44×44px tap target, aria-expanded, Svelte slide transition
  Semantic color tokens for dark mode compatibility
- Remove DocumentBottomPanel from document detail page
  Bottom panel replaced by topbar drawer for metadata access
  Simplify +page.server.ts (remove comments loading)
  Update page.server.spec.ts for new load signature

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

frontend/src/routes/documents/[id]/+page.svelte

@@ -3,9 +3,7 @@ import { onMount } from 'svelte';
 import { page } from '$app/state';
 import DocumentTopBar from '$lib/components/DocumentTopBar.svelte';
 import DocumentViewer from '$lib/components/DocumentViewer.svelte';
-import DocumentBottomPanel from '$lib/components/DocumentBottomPanel.svelte';
 import AnnotationSidePanel from '$lib/components/AnnotationSidePanel.svelte';
-import type { DocumentPanelTab } from '$lib/types';
 
 let { data } = $props();
 
@@ -62,38 +60,17 @@ let annotateMode = $state(false);
 let activeAnnotationId = $state<string | null>(null);
 let activeAnnotationPage = $state<number | null>(null);
 
-// Close the panel when entering annotate mode so the PDF is fully visible.
-$effect(() => {
-	if (annotateMode) panelOpen = false;
-});
+// ── Navigation / init ─────────────────────────────────────────────────────────
 
-// ── Bottom panel state ────────────────────────────────────────────────────────
-
-let panelOpen = $state(false);
-let panelHeight = $state(0); // set to full height on mount
 let navHeight = $state(0);
-let activeTab = $state<DocumentPanelTab>('metadata');
 
 onMount(() => {
 	navHeight = document.querySelector('header')?.getBoundingClientRect().height ?? 0;
 
-	const topbar = document.querySelector('[data-topbar]');
-	panelHeight = window.innerHeight - navHeight - (topbar?.getBoundingClientRect().height ?? 0);
-
 	if (targetAnnotationId) {
-		// Deep-link into an annotation comment: open the side panel
 		activeAnnotationId = targetAnnotationId;
-	} else if (targetCommentId) {
-		// Deep-link into a document-level comment: open discussion tab
-		panelOpen = true;
-		activeTab = 'discussion';
-	} else if (!doc?.filePath) {
-		// No file yet — open to metadata so the panel is immediately useful.
-		panelOpen = true;
-		activeTab = 'metadata';
 	}
 
-	// Track last-visited document for the dashboard resume strip
 	if (doc?.id) {
 		localStorage.setItem(
 			'familienarchiv.lastVisited',
@@ -106,8 +83,6 @@ onMount(() => {
 			if (activeAnnotationId) {
 				activeAnnotationId = null;
 				activeAnnotationPage = null;
-			} else if (panelOpen) {
-				panelOpen = false;
 			}
 		}
 	}
@@ -160,16 +135,4 @@ onMount(() => {
 			}}
 		/>
 	</div>
-
-	<DocumentBottomPanel
-		doc={doc}
-		comments={(data.comments ?? []) as never[]}
-		canComment={canComment}
-		currentUserId={currentUserId}
-		canAdmin={canAdmin}
-		targetCommentId={targetCommentId}
-		bind:open={panelOpen}
-		bind:height={panelHeight}
-		bind:activeTab={activeTab}
-	/>
 </div>