feat(c6): notificações e push — Web Push VAPID, badge dinâmico, Share API

FR-6.1/6.2: Sandra recebe push quando pedido entra em pending_approval;
Rafael recebe quando pedido é aprovado ou recusado. Service worker registrado
em background (PWA-ready via public/sw.js).

FR-6.3: Badge na Topbar busca GET /notifications/pending-count (supervisores
veem count de pending_approval; reps veem 0). Intervalo de 30s.

FR-6.4: Botão Compartilhar no OrderDetailPage para pedidos approved/invoiced
(apenas reps). Usa navigator.share() com texto formatado para WhatsApp.

Infra: modelo PushSubscription (Prisma), NotificationsModule (subscribe/
unsubscribe/pending-count + PushService VAPID), VAPID keys em .env,
integração no OrdersService (create → supervisores, approve/reject → repId).

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

apps/api/prisma/migrations/20260528121304_c6_push_subscriptions/migration.sql

@@ -0,0 +1,22 @@
+-- CreateTable
+CREATE TABLE "PushSubscription" (
+    "id" UUID NOT NULL,
+    "userId" TEXT NOT NULL,
+    "role" TEXT NOT NULL,
+    "endpoint" TEXT NOT NULL,
+    "p256dh" TEXT NOT NULL,
+    "auth" TEXT NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "PushSubscription_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "PushSubscription_endpoint_key" ON "PushSubscription"("endpoint");
+
+-- CreateIndex
+CREATE INDEX "PushSubscription_userId_idx" ON "PushSubscription"("userId");
+
+-- CreateIndex
+CREATE INDEX "PushSubscription_role_idx" ON "PushSubscription"("role");