Bygg NeuroSemantics AI: minimal mobilapp, en backend, IaC och CI/CD

Ersätter den tidigare webappen på denna branch med ett fokuserat monorepo:

- apps/mobile: Expo/React Native med tre vyer (Welcome, Chat, Paywall),
  Cognito hosted UI-inloggning (Apple/Google/e-post) och In-App
  Purchase/Play Billing via en gemensam purchases-modul.
- services/api: en enda Lambda-backend — OpenAI Responses API med
  Markdown-kunskapsbas som systeminstruktioner, free tier-gräns i
  PostgreSQL (HTTP 402 -> paywall) och kvittoverifiering bakom ett
  delat PaymentProvider-interface (Apple/Google, Stripe kan läggas
  till för webb senare).
- infra: AWS CDK-stack med API Gateway (JWT-authorizer), Lambda,
  Cognito, Aurora Serverless v2 och Secrets Manager.
- db/migrations: minimal datamodell (users + usage), inga
  konversationer sparas.
- GitHub Actions: CI (lint, typecheck, test) och deploy från main.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0118DaxZR36RpnY524vRqx3z

apps/mobile/src/purchases/index.ts

@@ -0,0 +1,67 @@
+import { Platform } from 'react-native';
+import {
+  endConnection,
+  getAvailablePurchases,
+  initConnection,
+  requestSubscription,
+  type SubscriptionPurchase,
+} from 'react-native-iap';
+import { verifyPurchase } from '../api/client';
+import { appConfig } from '../config';
+
+export type Plan = 'monthly' | 'yearly';
+
+const platform: 'ios' | 'android' = Platform.OS === 'ios' ? 'ios' : 'android';
+
+export function productIdFor(plan: Plan): string {
+  if (platform === 'ios') {
+    return plan === 'monthly' ? appConfig.iosMonthlyProductId : appConfig.iosYearlyProductId;
+  }
+  return plan === 'monthly' ? appConfig.androidMonthlyProductId : appConfig.androidYearlyProductId;
+}
+
+function receiptOf(purchase: SubscriptionPurchase): string {
+  // iOS: base64 app receipt. Android: Play Billing purchase token.
+  return platform === 'ios' ? purchase.transactionReceipt : (purchase.purchaseToken ?? '');
+}
+
+async function withConnection<T>(fn: () => Promise<T>): Promise<T> {
+  await initConnection();
+  try {
+    return await fn();
+  } finally {
+    await endConnection();
+  }
+}
+
+/**
+ * Runs the native purchase flow, then lets the backend verify the receipt
+ * with the store. Returns the resulting subscription status.
+ */
+export async function purchase(plan: Plan): Promise<'free' | 'active'> {
+  const productId = productIdFor(plan);
+  return withConnection(async () => {
+    await requestSubscription({ sku: productId });
+    const purchases = await getAvailablePurchases();
+    const match = purchases.find((p) => p.productId === productId);
+    if (!match) throw new Error('Purchase not found after transaction');
+    const result = await verifyPurchase({ platform, productId, receipt: receiptOf(match) });
+    return result.subscriptionStatus;
+  });
+}
+
+/** Re-checks existing purchases with the store ("Restore Purchase"). */
+export async function restore(): Promise<'free' | 'active'> {
+  return withConnection(async () => {
+    const purchases = await getAvailablePurchases();
+    for (const p of purchases) {
+      const result = await verifyPurchase({
+        platform,
+        productId: p.productId,
+        receipt: receiptOf(p),
+      });
+      if (result.subscriptionStatus === 'active') return 'active';
+    }
+    return 'free';
+  });
+}