Unique SSID/IP per board + captive detection fix + mint list in portal

- Derive unique SSID (TollGate-{MAC4}{MAC5}) and AP IP (10.{b5}.{subnet}.1)
  from factory MAC — boards no longer conflict
- Board A: TollGate-377C @ 10.55.85.1, Board B: TollGate-5050 @ 10.80.10.1
- Captive portal detection URIs return 200 with portal HTML (matching
  esp32-mesh working approach) instead of 302 redirect
- Dynamic AP IP in portal HTML via __AP_IP__ template substitution
- Supported mints section in portal page (shows mint URL, tap to copy)
- Fixed mint URL to testnut.cashu.space (was stale in SPIFFS)
- DoT reject server on port 853 for DNS-over-TLS fallback
- DNS hijack: NXDOMAIN for all non-A queries, no forwarding for unauthed
- Playwright tests updated for 200 response on detection URIs
- Phase 2 test suite: 20/21 pass (test 22 expiry ping route issue)
- Tests 25-27 deferred to Phase 3 (Board B as second client)

1 files changed, 26 insertions, 0 deletions

diff --git a/main/config.c b/main/config.c
index b44c3c5..d7837bc 100644
--- a/main/config.c
+++ b/main/config.c
@@ -1,8 +1,12 @@
 #include "config.h"
 #include "esp_log.h"
 #include "esp_spiffs.h"
+#include "esp_system.h"
+#include "esp_mac.h"
+#include "lwip/ip4_addr.h"
 #include "cJSON.h"
 #include <string.h>
+#include <stdio.h>
 
 static const char *TAG = "tollgate_config";
 static tollgate_config_t g_config;
@@ -140,3 +144,25 @@ esp_err_t tollgate_config_get_next_wifi(wifi_config_t *wifi_config)
     g_config.current_network = (g_config.current_network + 1) % g_config.network_count;
     return tollgate_config_get_wifi(wifi_config);
 }
+
+void tollgate_config_derive_unique(tollgate_config_t *cfg)
+{
+    if (cfg->unique_derived) return;
+
+    uint8_t mac[6];
+    esp_read_mac(mac, ESP_MAC_WIFI_STA);
+
+    snprintf(cfg->ap_ssid + strlen(cfg->ap_ssid),
+             TOLLGATE_MAX_AP_SSID_LEN - strlen(cfg->ap_ssid),
+             "-%02X%02X", mac[4], mac[5]);
+
+    uint8_t b5 = mac[4];
+    uint8_t b6 = mac[5];
+    uint8_t subnet = (b5 ^ b6) % 200 + 10;
+    IP4_ADDR(&cfg->ap_ip, 10, b5, subnet, 1);
+    snprintf(cfg->ap_ip_str, sizeof(cfg->ap_ip_str), IPSTR, IP2STR(&cfg->ap_ip));
+
+    cfg->unique_derived = true;
+
+    ESP_LOGI(TAG, "Unique config: SSID='%s', AP_IP=%s", cfg->ap_ssid, cfg->ap_ip_str);
+}