feat: WiFi beacon price discovery via Vendor IE (two-board verified)

Price discovery allows TollGate ESP32 boards to advertise their per-step
price via WiFi Vendor-Specific Information Elements (OUI 0xC0FFEE) in
beacon and probe response frames. Nearby boards passively scan and build
a market view of competing TollGates without requiring internet access.

Features:
- beacon_price.c/h: 26-byte packed Vendor IE payload (price, step, metric,
  mint_hash, geohash, npub_hash), injected via esp_wifi_set_vendor_ie()
- market.c/h: Passive WiFi scan receiver, vendor IE callback parsing,
  BSSID-correlated market entries, effective price ranking
- GET /market API endpoint: JSON market snapshot with discovered entries
- AP-only services: beacon + market + API start on WIFI_EVENT_AP_START,
  independent of STA connectivity
- STA reconnect fix: 2s delay between retries creates scan windows;
  s_sta_connecting guard prevents double-connect
- write-config-ap-only-a/b Makefile targets for STA-less testing
- market_tick() in main loop, client price comparison logging

Hardware verified: both boards discover each other via Vendor IE beacons.
Board A sees TollGate-C0E9CA (RSSI=-30), Board B sees TollGate-B96D80
(RSSI=-25). test-market.mjs: 9/9, test-price-discovery.mjs: 7/7 per board.

Unit tests: 45 new assertions across test_beacon_price (28) and test_market
(17). All 15 test suites pass. ESP-IDF build clean for ESP32-S3.

1 files changed, 2 insertions, 1 deletions

diff --git a/main/cvm_server.c b/main/cvm_server.c
index 644738b..a4804d2 100644
--- a/main/cvm_server.c
+++ b/main/cvm_server.c
@@ -8,6 +8,7 @@
 #include "nucula_wallet.h"
 #include "cJSON.h"
 #include "esp_log.h"
+#include "esp_timer.h"
 #include "esp_tls.h"
 #include "esp_crt_bundle.h"
 #include "esp_random.h"
@@ -576,7 +577,7 @@ static void cvm_relay_task(void *arg)
                     char *text = parse_ws_text_frame(buf, rlen);
                     if (text) {
                         if (strlen(text) > 0) {
-                            process_relay_message(tls, relay_url, text);
+                            process_relay_message(relay_url, text);
                         }
                         free(text);
                     }