Phase 4

Seed data extended with a second barber (different hours/services), a beard-trim service + category, breaks, time off, a guest customer, and appointments in all three key states — verified against a live throwaway Postgres.
14 new integration tests (38 total with Phase 3's) covering guest/authenticated booking, any-barber assignment, slot-conflict handling, ownership enforcement, guest-data isolation, and book-again repricing.
Playwright E2E suite for the 6 required customer journeys, with its own global-setup.ts that migrates and seeds a database automatically.
Full verification pass, which caught and fixed three real bugs along the way (not just test-workarounds):
A date off-by-one bug in the calendar picker that made real weekdays show as closed for anyone in a UTC+ timezone (including the business's own).
A dialog that could vanish mid-confirmation on cancellation, before the customer could read the late-cancellation notice.
A silent test-cleanup leak in the Phase 3 fixtures that had been leaking stray businesses since Phase 3.
Plus a baseline desktop-responsive fix (centered max-w-2xl columns) across Home/Appointments/Settings/booking flow, since desktop had been effectively unstyled.
Final state: 90 unit tests, 38 integration tests, and all 6 E2E journeys passing together on a fresh database; clean tsc, eslint, and next build. Full writeup with routes, security model, guest-matching rules, known limitations, and what to check before Phase 5 is in docs/phase-4-summary.md.

src/app/appointments/[id]/reschedule/layout.tsx

@@ -0,0 +1,13 @@
+/**
+ * Deliberately OUTSIDE the (customer) route group, same reasoning as
+ * src/app/book/layout.tsx: this page reuses BarberDateTimePicker, which
+ * renders its own fixed bottom action bar. Nested under (customer)'s
+ * persistent BottomNav, the two fixed-bottom elements would overlap —
+ * the nav (z-50) sits above the picker's "Confirm Reschedule" bar (z-40)
+ * and swallows clicks meant for it. Hiding the bottom nav here avoids
+ * that collision, matching the booking flow's own "may temporarily hide
+ * the bottom navigation" allowance.
+ */
+export default function RescheduleLayout({ children }: { children: React.ReactNode }) {
+  return <div className="min-h-screen bg-stone">{children}</div>;
+}