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.server.ts

@@ -1,17 +1,12 @@
 import { error, redirect } from '@sveltejs/kit';
-import { env } from '$env/dynamic/private';
 import { createApiClient } from '$lib/api.server';
 import { getErrorMessage } from '$lib/errors';
 
 export async function load({ params, fetch }) {
 	const { id } = params;
 	const api = createApiClient(fetch);
-	const base = env.API_INTERNAL_URL || 'http://localhost:8080';
 
-	const [docResult, commentsRes] = await Promise.all([
-		api.GET('/api/documents/{id}', { params: { path: { id } } }),
-		fetch(`${base}/api/documents/${id}/comments`).catch(() => null)
-	]);
+	const docResult = await api.GET('/api/documents/{id}', { params: { path: { id } } });
 
 	if (docResult.response.status === 401) throw redirect(302, '/login');
 
@@ -20,14 +15,5 @@ export async function load({ params, fetch }) {
 		throw error(docResult.response.status, getErrorMessage(code));
 	}
 
-	let comments: unknown[] = [];
-	if (commentsRes?.ok) {
-		try {
-			comments = await commentsRes.json();
-		} catch {
-			// ignore invalid response
-		}
-	}
-
-	return { document: docResult.data!, comments };
+	return { document: docResult.data! };
 }