Phase 3: on-device Cashu wallet with mbedTLS secp256k1 + SPIFFS persistence + PSRAM

- wallet.c/h: secp256k1 ECP primitives (hash_to_curve, scalar_mul, point_add)
- wallet_persist.c/h: SPIFFS persistence with threshold-based write protection
- Fee accounting for swap (input_fee_ppk from /v1/keysets)
- Keyset fetch via /v1/keysets (586 bytes vs 21KB for /v1/keys)
- Wallet API: GET /wallet, POST /wallet/swap, POST /wallet/send
- Payment proofs auto-stored to wallet + persisted on SPIFFS
- PSRAM enabled for large allocations (ESP32-S3 has 8MB)
- Wallet init deferred to dedicated task (avoids sys_evt stack overflow)
- Cashu proof ID buffer size fixed (66 hex chars, not 16)
- HTTP client: added fetch_headers() call for proper response handling
- persist_threshold_sats config parameter (default: 1 sat)

1 files changed, 11 insertions, 0 deletions

diff --git a/main/tollgate_main.c b/main/tollgate_main.c
index 9d2c392..d4b29bc 100644
--- a/main/tollgate_main.c
+++ b/main/tollgate_main.c
@@ -16,6 +16,7 @@
 #include "firewall.h"
 #include "session.h"
 #include "tollgate_api.h"
+#include "wallet.h"
 
 #define MAX_STA_RETRY 5
 static const char *TAG = "tollgate_main";
@@ -88,6 +89,14 @@ static void ip_event_handler(void *arg, esp_event_base_t event_base,
     }
 }
 
+static void wallet_init_task(void *pvParameters)
+{
+    const tollgate_config_t *cfg = tollgate_config_get();
+    wallet_init();
+    wallet_fetch_keysets(cfg->mint_url);
+    vTaskDelete(NULL);
+}
+
 static void start_services(void)
 {
     if (s_services_mutex) xSemaphoreTake(s_services_mutex, portMAX_DELAY);
@@ -107,6 +116,8 @@ static void start_services(void)
     firewall_init(ap_ip_info.ip);
     session_manager_init();
 
+    xTaskCreate(wallet_init_task, "wallet_init", 32768, NULL, 5, NULL);
+
     const tollgate_config_t *cfg = tollgate_config_get();
     dns_server_start(ap_ip_info.ip, upstream_dns);
     captive_portal_start(cfg->ap_ip_str);