rebuild the app on a typed, modular structure wired to the real API

The whole app lived in one 3,071-line App.tsx on a Figma scaffold (60 unused
packages, 45 unused UI components, no type-check). The live site could not
reach the backend, Persian-keyboard digits were erased from the phone field,
guests were signed out after an hour, "mark read" hit a method the server
does not accept (405), and iOS Safari blocked the payment window.

What changed:
- src/ split into api/ (one typed client: timeouts, GET retry, single-flight
  refresh, SSE), screens/ (one file each), components/, state/, nav/, lib/.
- The API address is configuration only: public/config.js at runtime, then
  VITE_API_BASE_URL at build time, then same-origin /api. No domain in code.
- Responsive shell instead of a fixed 390x844 phone frame; self-hosted
  Vazirmatn instead of Google Fonts; strict TypeScript, `npm run build`
  type-checks first.
- Everything on the handoff list: tutor answers keep their line breaks, have
  thumbs up/down, follow-ups, "from the book" badge, retry, history that
  survives tab switches and reloads, "why was I wrong" from a wrong answer
  with questionId; question reports; hearts with maxHearts/unlimited and a
  no-hearts screen with the refill time; result screen and a visible error
  when lesson completion fails; subscription status, badge, discount code
  before the gateway and the payment-return message; guest refresh token;
  6-digit OTP with resend timer; age saved as a Jalali birthYear; PATCH
  read-all; leaderboard refetched on open with "you" highlighted; selected
  companion shown across the app; logout that revokes the refresh token.
- New screens for endpoints that had none: profile, streak calendar,
  support tickets and bug reports, parents, invite-a-friend (with ?ref=
  tracking), guest-to-phone upgrade.
- Browser/phone back button walks the screen stack.

Checked with a headless-Chrome walkthrough against a local backend at
390x844 and 360x740 (fresh guest: onboarding, setup, a full lesson, map,
island sheet, every tab and sub-screen, one real tutor question, reload,
logout): no console errors, no failed API calls. Real SMS login and a real
Zarinpal payment were not exercised.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/lib/errors.ts

@@ -0,0 +1,11 @@
+import { ApiError } from '@/api';
+
+/** پیامِ قابلِ فهم برای دانش‌آموز، از هر خطایی. */
+export function friendlyError(err: unknown, fallback = 'یه مشکلی پیش اومد، دوباره امتحان کن'): string {
+  if (!(err instanceof ApiError)) return fallback;
+  if (err.isNetwork) return 'ارتباط با سرور برقرار نشد؛ اینترنتت رو چک کن';
+  if (err.isRateLimited) return err.detail && !err.detail.startsWith('خطای') ? err.detail : 'زیادی تلاش کردی؛ چند لحظه صبر کن';
+  if (err.isProviderDown) return 'این سرویس الان در دسترس نیست؛ کمی بعد دوباره امتحان کن';
+  if (err.status >= 500) return 'سرور موقتاً مشکل داره؛ کمی بعد دوباره امتحان کن';
+  return err.detail || fallback;
+}