feat: multi-mint wallet with health tracking, WPA auto-detect, display gating

Squash merge of feature/multi-mint-support (21 commits):

Multi-mint wallet:
- Accept payments from 4 mints: minibits, coinos, 21mint, lnvoltz
- Periodic health probing (300s interval, 3 recovery threshold)
- Multi-wallet init with nucula_wallet_init_multi()
- /mints and /wallet API endpoints

WPA auto-detect:
- wifi_auth_mode config field (default WPA2, supports WPA3)
- Runtime mapping to wifi_auth_mode_t in STA config

Display gating:
- display_enabled config field (default true)
- Guards display_init/display_update per-board

Bug fixes:
- 3s delay before service start prevents lwip mem_free assertion
- Real npub in discovery (identity_get()->npub_hex)
- Health probe interval 300s (production value)
- Duplicate services_start_task call removed
- UTF-8 arrow replaced with ASCII in log message

Tests: 61+14 unit tests passing, firmware builds clean

1 files changed, 1 insertions, 7 deletions

diff --git a/main/wifistr.c b/main/wifistr.c
index 543aaf6..bf03b4d 100644
--- a/main/wifistr.c
+++ b/main/wifistr.c
@@ -2,7 +2,6 @@
 #include "identity.h"
 #include "nostr_event.h"
 #include "config.h"
-#include "local_relay.h"
 #include "esp_log.h"
 #include "esp_tls.h"
 #include "esp_crt_bundle.h"
@@ -217,13 +216,8 @@ esp_err_t wifistr_publish(void)
 
     ESP_LOGI(TAG, "Wifistr event: %s", event_json);
 
-    esp_err_t local_ret = local_relay_publish(event_json, strlen(event_json));
-    if (local_ret == ESP_OK) {
-        ESP_LOGI(TAG, "Published to local relay");
-    }
-
     const tollgate_config_t *cfg = tollgate_config_get();
-    esp_err_t last_err = local_ret;
+    esp_err_t last_err = ESP_FAIL;
 
     for (int i = 0; i < cfg->nostr_relay_count; i++) {
         esp_err_t err = ws_send_to_relay(cfg->nostr_relays[i], event_json);