fix: merge readiness — display_enabled config, real pubkey, probe interval, dedup services

- Add display_enabled config field (default true, parsed from config.json)
- Guard display_init/display_update behind display_enabled check
- Fix discovery pubkey: replace hardcoded all-zeros with identity_get()->npub_hex
- Revert MINT_HEALTH_PROBE_INTERVAL_S from 30 (testing) to 300 (production)
- Remove duplicate services_start_task call in IP event handler
- Fix UTF-8 arrow in STA auth threshold log message
- Gitignore compiled test binaries (test_mcp_handler, test_mint_health, etc.)
- Remove tracked test binaries from git

Verified on Board B (stable):
- make test-discovery-b: pubkey=d6bfe100..., metric=milliseconds, price_per_step tags
- make test-mints-b: 4 mints listed with reachable field
- Wallet: 40 sats balance with 4 proofs from previous payment
- All API endpoints responding (discovery, mints, wallet, whoami, portal)
- 75/75 unit tests passing

1 files changed, 5 insertions, 1 deletions

diff --git a/main/config.c b/main/config.c
index fe0ceba..22b26da 100644
--- a/main/config.c
+++ b/main/config.c
@@ -36,6 +36,7 @@ esp_err_t tollgate_config_init(void)
     g_config.cvm_enabled = true;
     strncpy(g_config.cvm_relays, "wss://relay.primal.net", sizeof(g_config.cvm_relays) - 1);
     strncpy(g_config.wifi_auth_mode, "WPA2", sizeof(g_config.wifi_auth_mode) - 1);
+    g_config.display_enabled = true;
 
     esp_vfs_spiffs_conf_t conf = {
         .base_path = "/spiffs",
@@ -278,6 +279,9 @@ esp_err_t tollgate_config_init(void)
         strncpy(g_config.wifi_auth_mode, auth_mode->valuestring, sizeof(g_config.wifi_auth_mode) - 1);
     }
 
+    cJSON *disp_en = cJSON_GetObjectItem(root, "display_enabled");
+    if (disp_en && cJSON_IsBool(disp_en)) g_config.display_enabled = cJSON_IsTrue(disp_en);
+
     if (g_config.payout.mint_count == 0 && g_config.mint_url[0] != '\0') {
         strncpy(g_config.payout.mints[0].url, g_config.mint_url,
                 sizeof(g_config.payout.mints[0].url) - 1);
@@ -331,7 +335,7 @@ esp_err_t tollgate_config_get_wifi(wifi_config_t *wifi_config)
     } else if (strstr(g_config.wifi_auth_mode, "WPA2")) {
         wifi_config->sta.threshold.authmode = WIFI_AUTH_WPA2_PSK;
     }
-    ESP_LOGI(TAG, "STA auth threshold: %s → %d", g_config.wifi_auth_mode, wifi_config->sta.threshold.authmode);
+    ESP_LOGI(TAG, "STA auth threshold: %s -> %d", g_config.wifi_auth_mode, wifi_config->sta.threshold.authmode);
     return ESP_OK;
 }