Add Stripe embedded onboarding

- Update StripeConnectOnboarding component with embedded flow
- Add new Stripe routes and service methods for embedded onboarding
- Update EarningsStatus and EarningsDashboard to support new flow
- Add required frontend dependencies

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/services/api.ts

@@ -309,6 +309,7 @@ export const stripeAPI = {
   createConnectedAccount: () => api.post("/stripe/accounts"),
   createAccountLink: (data: { refreshUrl: string; returnUrl: string }) =>
     api.post("/stripe/account-links", data),
+  createAccountSession: () => api.post("/stripe/account-sessions"),
   getAccountStatus: () => api.get("/stripe/account-status"),
   createSetupCheckoutSession: (data: { rentalData?: any }) =>
     api.post("/stripe/create-setup-checkout-session", data),