refactor(persons): extract PersonCard, PersonMergePanel, CoCorrespondentsList, PersonDocumentList

Split the 610-line person detail page into four focused co-located components:
- PersonCard: view/edit card with inline form (owns editMode)
- PersonMergePanel: merge target typeahead + two-step confirm (state reset via {#key})
- CoCorrespondentsList: frequency-ranked correspondent chips linking to conversations
- PersonDocumentList: reusable sorted/paginated document list (used for sent + received)

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

frontend/src/routes/persons/[id]/PersonMergePanel.svelte

@@ -0,0 +1,83 @@
+<script lang="ts">
+import { enhance } from '$app/forms';
+import PersonTypeahead from '$lib/components/PersonTypeahead.svelte';
+import { m } from '$lib/paraglide/messages.js';
+
+let {
+	person,
+	form
+}: {
+	person: { firstName: string; lastName: string };
+	form?: { mergeError?: string } | null;
+} = $props();
+
+let mergeTargetId = $state('');
+let showMergeConfirm = $state(false);
+</script>
+
+<div class="mb-10 overflow-hidden rounded-sm border border-line bg-surface shadow-sm">
+	<div class="p-6 md:p-8">
+		<h2 class="mb-1 font-serif text-lg text-ink">{m.person_merge_heading()}</h2>
+		<p class="mb-5 font-sans text-sm text-ink-2">
+			{m.person_merge_description()}
+		</p>
+
+		{#if form?.mergeError}
+			<p class="mb-4 rounded border border-red-200 bg-red-50 px-3 py-2 text-sm text-red-600">
+				{form.mergeError}
+			</p>
+		{/if}
+
+		<form method="POST" action="?/merge" use:enhance>
+			<input type="hidden" name="targetPersonId" bind:value={mergeTargetId} />
+
+			<div class="flex flex-col items-end gap-3 sm:flex-row">
+				<div class="flex-1">
+					<PersonTypeahead
+						name="_targetPersonDisplay"
+						label={m.person_merge_target_label()}
+						value={mergeTargetId}
+						onchange={(value) => {
+							mergeTargetId = value;
+							showMergeConfirm = false;
+						}}
+					/>
+				</div>
+
+				{#if !showMergeConfirm}
+					<button
+						type="button"
+						disabled={!mergeTargetId}
+						onclick={() => (showMergeConfirm = true)}
+						class="rounded border border-red-300 px-4 py-2 text-sm font-bold tracking-widest text-red-600 uppercase transition-colors hover:bg-red-50 disabled:cursor-not-allowed disabled:opacity-40"
+					>
+						{m.person_btn_merge()}
+					</button>
+				{:else}
+					<div class="flex gap-2">
+						<button
+							type="submit"
+							class="rounded bg-red-600 px-4 py-2 text-sm font-bold tracking-widest text-white uppercase transition-colors hover:bg-red-700"
+						>
+							{m.person_btn_merge_confirm()}
+						</button>
+						<button
+							type="button"
+							onclick={() => (showMergeConfirm = false)}
+							class="rounded border border-line px-4 py-2 text-sm font-bold tracking-widest text-ink-2 uppercase transition-colors hover:bg-muted"
+						>
+							{m.btn_cancel()}
+						</button>
+					</div>
+				{/if}
+			</div>
+
+			{#if showMergeConfirm}
+				<p class="mt-3 rounded border border-red-200 bg-red-50 px-3 py-2 text-sm text-red-700">
+					{m.person_merge_warning()} <strong>{person.firstName} {person.lastName}</strong>
+					{m.person_merge_will_be_deleted()}
+				</p>
+			{/if}
+		</form>
+	</div>
+</div>