feat(mvp-rep): formas de pagamento do ERP + suporte offline completo

Formas de pagamento:
- Endpoint GET /catalog/payment-methods lendo vw_formas_pagamento
  filtrado por ativa=1 e integrar_sar=1
- FormaPagamento schema/type no shared api-interface
- Hook useFormasPagamento (staleTime 1h) substituindo lista hardcoded

Offline (FR-4.2 / NFR-2.1–2.4):
- IndexedDB queue: lib/offline/idb.ts + order-queue.ts sem deps externos
- NewOrderPage detecta !navigator.onLine → enqueueOrder() → toast + reset
- useOfflineSync: auto-sync ao reconectar (POST orders + PATCH transmit)
- usePendingOrders: fila reativa via CustomEvents
- AppShell: banner offline + useOfflineSync() global
- OrdersPage: seção de pedidos pendentes com retry/descartar
- sw.js: network-first para API GETs cacheáveis + stale-while-revalidate
  para assets + app shell navigate fallback

Docs:
- architecture.md: documento de decisões de arquitetura do SAR MVP

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

apps/web/public/sw.js

@@ -1,5 +1,106 @@
-// Service Worker SAR — C6 Web Push
-// Recebe push events e exibe notificação nativa. Clique abre a URL do payload.
+// Service Worker SAR
+// C4/NFR-2: cache de API para uso offline (network-first, fallback to cache)
+// C6: Web Push
+// App shell: stale-while-revalidate para assets estáticos
+
+const API_CACHE = 'sar-api-v2';
+const SHELL_CACHE = 'sar-shell-v2';
+
+// Paths de API que valem ser cacheados para offline
+// Auth e mutations (POST/PATCH) nunca são interceptados
+const CACHEABLE_API = [
+  '/api/v1/clients',
+  '/api/v1/catalog',
+  '/api/v1/orders',
+  '/api/v1/dashboard',
+  '/api/v1/auth/me',
+];
+
+// ── Fetch ──────────────────────────────────────────────────────────────────────
+
+self.addEventListener('fetch', (event) => {
+  const { request } = event;
+  if (request.method !== 'GET') return;
+
+  const url = new URL(request.url);
+
+  if (url.pathname.startsWith('/api/v1/')) {
+    const cacheable = CACHEABLE_API.some((p) => url.pathname.startsWith(p));
+    if (cacheable) {
+      event.respondWith(networkFirst(request, API_CACHE));
+    }
+    return;
+  }
+
+  if (request.mode === 'navigate') {
+    // App shell HTML — network first, cache fallback
+    event.respondWith(shellNavigate(request));
+    return;
+  }
+
+  // Assets estáticos (JS/CSS/fontes/imagens) — stale-while-revalidate
+  if (/\.(js|css|woff2?|png|svg|ico)$/.test(url.pathname)) {
+    event.respondWith(staleWhileRevalidate(request, SHELL_CACHE));
+  }
+});
+
+// Network-first: tenta rede, cai no cache se offline
+async function networkFirst(request, cacheName) {
+  const cache = await caches.open(cacheName);
+  try {
+    const response = await fetch(request);
+    if (response.ok) {
+      cache.put(request, response.clone());
+    }
+    return response;
+  } catch {
+    const cached = await cache.match(request);
+    if (cached) return cached;
+    return offlineResponse();
+  }
+}
+
+// Navigate: network first; fallback para a raiz cacheada
+async function shellNavigate(request) {
+  const cache = await caches.open(SHELL_CACHE);
+  try {
+    const response = await fetch(request);
+    if (response.ok) {
+      cache.put(request, response.clone());
+      // Sempre armazena a raiz como fallback universal
+      cache.put(new Request('/'), response.clone());
+    }
+    return response;
+  } catch {
+    const cached = (await cache.match(request)) ?? (await cache.match('/'));
+    if (cached) return cached;
+    return offlineResponse();
+  }
+}
+
+// Stale-while-revalidate: responde do cache, atualiza em background
+async function staleWhileRevalidate(request, cacheName) {
+  const cache = await caches.open(cacheName);
+  const cached = await cache.match(request);
+  const networkFetch = fetch(request).then((response) => {
+    if (response.ok) cache.put(request, response.clone());
+    return response;
+  });
+  return cached ?? networkFetch;
+}
+
+function offlineResponse() {
+  return new Response(
+    JSON.stringify({
+      type: 'sar:offline',
+      title: 'Sem conexão',
+      status: 503,
+    }),
+    { status: 503, headers: { 'Content-Type': 'application/json' } },
+  );
+}
+
+// ── Push (C6) ─────────────────────────────────────────────────────────────────
 
 self.addEventListener('push', (event) => {
   const data = event.data?.json() ?? {};