Sync display with live TollGate state

- Periodic refresh: wallet balance + client count every 5s from main loop
- display_notify_payment() API: passes payment amount and time allotment
- tollgate_api.c: triggers PAYMENT_RECEIVED state after wallet receive
- AP station events update client count in real-time
- Config data (price, mint) passed to display during boot phase
- Payment screen shows actual sats paid and time purchased
- Updated DISPLAY_UI_PLAN.md with state-sync audit and checklist

1 files changed, 1 insertions, 0 deletions

diff --git a/main/display.h b/main/display.h
index 1530e57..49b3ffd 100644
--- a/main/display.h
+++ b/main/display.h
@@ -23,6 +23,7 @@ void display_update(const char *ap_ssid, int active_clients,
                     uint64_t wallet_balance, const char *portal_url,
                     const char *mint_url, int price_per_step,
                     const char *wifi_status);
+void display_notify_payment(int amount_sats, int64_t allotment_ms);
 void display_render_text(int x, int y, const char *text, uint16_t fg, uint16_t bg, int scale);
 void display_render_qr(const char *text);