feat: implement Phase 4 SvelteKit frontend + backend enhancements

Backend:
- Add dashboard API (today stats, inbox count, law alerts, pipeline status)
- Add /api/documents/tree endpoint for sidebar domain/sub_group tree
- Migrate auth to HttpOnly cookie for refresh token (XSS defense)
- Add /api/auth/logout endpoint (cookie cleanup)
- Register dashboard router in main.py

Frontend (SvelteKit + Tailwind CSS v4):
- api.ts: fetch wrapper with refresh queue pattern, 401 single retry,
  forced logout on refresh failure
- Auth store: login/logout/refresh with memory-based access token
- UI store: toast system, sidebar state
- Login page with TOTP support
- Dashboard with 4 stat widgets + recent documents
- Document list with hybrid search (debounce, URL query state, mode select)
- Document detail with format-aware viewer (markdown/PDF/HWP/Synology/fallback)
- Metadata panel (AI summary, tags, processing history)
- Inbox triage UI (batch select, confirm dialog, domain override)
- Settings page (password change, TOTP status)

Infrastructure:
- Enable frontend service in docker-compose
- Caddy path routing (/api/* → fastapi, / → frontend) + gzip

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -0,0 +1,192 @@
+<script>
+  import { onMount } from 'svelte';
+  import { api } from '$lib/api';
+  import { addToast } from '$lib/stores/ui';
+
+  let documents = [];
+  let loading = true;
+  let selected = new Set();
+
+  onMount(loadInbox);
+
+  async function loadInbox() {
+    loading = true;
+    try {
+      // Inbox 파일만 필터
+      const data = await api('/documents/?page_size=100');
+      documents = data.items.filter(d => d.file_path?.startsWith('PKM/Inbox/'));
+    } catch (err) {
+      addToast('error', 'Inbox 로딩 실패');
+    } finally {
+      loading = false;
+    }
+  }
+
+  function toggleSelect(id) {
+    if (selected.has(id)) selected.delete(id);
+    else selected.add(id);
+    selected = selected; // 반응성 트리거
+  }
+
+  function toggleAll() {
+    if (selected.size === documents.length) {
+      selected = new Set();
+    } else {
+      selected = new Set(documents.map(d => d.id));
+    }
+  }
+
+  let approving = false;
+  let showConfirm = false;
+
+  function startApprove() {
+    if (selected.size === 0) {
+      addToast('warning', '선택된 문서가 없습니다');
+      return;
+    }
+    showConfirm = true;
+  }
+
+  async function confirmApprove() {
+    showConfirm = false;
+    approving = true;
+    let success = 0;
+    const ids = [...selected];
+
+    for (const id of ids) {
+      try {
+        // AI 분류 결과 그대로 승인 (Inbox에서 이동은 classify_worker가 처리)
+        const doc = documents.find(d => d.id === id);
+        if (doc?.ai_domain) {
+          await api(`/documents/${id}`, {
+            method: 'PATCH',
+            body: JSON.stringify({ source_channel: 'inbox_route' }),
+          });
+          success++;
+        }
+      } catch { /* skip */ }
+    }
+
+    addToast('success', `${success}건 승인 완료`);
+    selected = new Set();
+    approving = false;
+    loadInbox();
+  }
+
+  async function updateDomain(id, domain) {
+    try {
+      await api(`/documents/${id}`, {
+        method: 'PATCH',
+        body: JSON.stringify({ ai_domain: domain }),
+      });
+      documents = documents.map(d => d.id === id ? { ...d, ai_domain: domain } : d);
+      addToast('success', '도메인 변경됨');
+    } catch {
+      addToast('error', '변경 실패');
+    }
+  }
+
+  const DOMAINS = [
+    'Knowledge/Philosophy',
+    'Knowledge/Language',
+    'Knowledge/Engineering',
+    'Knowledge/Industrial_Safety',
+    'Knowledge/Programming',
+    'Knowledge/General',
+    'Reference',
+  ];
+</script>
+
+<div class="min-h-screen">
+  <nav class="flex items-center justify-between px-6 py-3 border-b border-[var(--border)] bg-[var(--surface)]">
+    <div class="flex items-center gap-4">
+      <a href="/" class="text-lg font-semibold hover:text-[var(--accent)]">PKM</a>
+      <span class="text-[var(--text-dim)]">/</span>
+      <span>Inbox</span>
+      <span class="text-xs px-2 py-0.5 rounded-full bg-[var(--warning)] text-black">{documents.length}</span>
+    </div>
+    <div class="flex items-center gap-2">
+      <button onclick={toggleAll} class="px-3 py-1.5 text-xs bg-[var(--surface)] border border-[var(--border)] rounded-lg">
+        {selected.size === documents.length ? '전체 해제' : '전체 선택'}
+      </button>
+      <button
+        onclick={startApprove}
+        disabled={approving || selected.size === 0}
+        class="px-4 py-1.5 text-xs bg-[var(--accent)] text-white rounded-lg disabled:opacity-50"
+      >
+        {approving ? '처리 중...' : `선택 승인 (${selected.size})`}
+      </button>
+    </div>
+  </nav>
+
+  <div class="max-w-6xl mx-auto p-6">
+    {#if loading}
+      <div class="space-y-3">
+        {#each Array(3) as _}
+          <div class="bg-[var(--surface)] rounded-lg p-4 border border-[var(--border)] animate-pulse h-24"></div>
+        {/each}
+      </div>
+    {:else if documents.length === 0}
+      <div class="text-center py-20 text-[var(--text-dim)]">
+        <p class="text-lg">Inbox가 비어 있습니다</p>
+        <p class="text-sm mt-1">새 파일이 들어오면 자동으로 표시됩니다</p>
+      </div>
+    {:else}
+      <div class="space-y-3">
+        {#each documents as doc}
+          <div class="flex items-start gap-3 p-4 bg-[var(--surface)] border border-[var(--border)] rounded-lg" class:border-[var(--accent)]={selected.has(doc.id)}>
+            <input
+              type="checkbox"
+              checked={selected.has(doc.id)}
+              onchange={() => toggleSelect(doc.id)}
+              class="mt-1 accent-[var(--accent)]"
+            />
+            <div class="flex-1 min-w-0">
+              <div class="flex items-center gap-2 mb-1">
+                <span class="text-xs px-1.5 py-0.5 rounded bg-[var(--border)] text-[var(--text-dim)] uppercase">{doc.file_format}</span>
+                <a href="/documents/{doc.id}" class="text-sm font-medium hover:text-[var(--accent)] truncate">{doc.title || '제목 없음'}</a>
+              </div>
+              {#if doc.ai_summary}
+                <p class="text-xs text-[var(--text-dim)] truncate">{doc.ai_summary.slice(0, 120)}</p>
+              {/if}
+              <div class="flex items-center gap-2 mt-2">
+                <span class="text-xs text-[var(--text-dim)]">AI 분류:</span>
+                <select
+                  value={doc.ai_domain || ''}
+                  onchange={(e) => updateDomain(doc.id, e.target.value)}
+                  class="text-xs px-2 py-1 bg-[var(--bg)] border border-[var(--border)] rounded text-[var(--text)]"
+                >
+                  <option value="">미분류</option>
+                  {#each DOMAINS as d}
+                    <option value={d}>{d.replace('Knowledge/', '')}</option>
+                  {/each}
+                </select>
+                {#if doc.ai_tags?.length > 0}
+                  <div class="flex gap-1 ml-2">
+                    {#each doc.ai_tags.slice(0, 3) as tag}
+                      <span class="text-xs px-1.5 py-0.5 bg-[var(--bg)] rounded text-[var(--accent)]">{tag}</span>
+                    {/each}
+                  </div>
+                {/if}
+              </div>
+            </div>
+          </div>
+        {/each}
+      </div>
+    {/if}
+  </div>
+
+  <!-- 확인 다이얼로그 -->
+  {#if showConfirm}
+    <div class="fixed inset-0 bg-black/60 flex items-center justify-center z-50">
+      <div class="bg-[var(--surface)] rounded-xl border border-[var(--border)] p-6 max-w-sm w-full mx-4">
+        <h3 class="text-lg font-semibold mb-2">{selected.size}건을 승인합니다</h3>
+        <p class="text-sm text-[var(--text-dim)] mb-4">AI 분류 결과를 확정하고 Inbox에서 이동합니다.</p>
+        <div class="flex gap-2 justify-end">
+          <button onclick={() => showConfirm = false} class="px-4 py-2 text-sm bg-[var(--bg)] border border-[var(--border)] rounded-lg">취소</button>
+          <button onclick={confirmApprove} class="px-4 py-2 text-sm bg-[var(--accent)] text-white rounded-lg">승인</button>
+        </div>
+      </div>
+    </div>
+  {/if}
+</div>