Phase 3: Nostr identity derivation + wifistr service discovery

- Add identity.c/h: HMAC-SHA512 derivation from nsec → npub, STA/AP MAC, SSID, AP IP
- Add nostr_event.c/h: NIP-01 event serialization + Schnorr signing (BIP-340)
- Add geohash.c/h: lat/lon to geohash encoding
- Add wifistr.c/h: kind 38787 event builder + WebSocket publish to Nostr relays
- Update config.c/h: nsec-based identity, Nostr relay/geo config, remove static SSID/IP
- Replace custom mbedTLS wallet with nucula library (libsecp256k1)
- Remove wallet.c/h, wallet_persist.c/h (replaced by nucula_lib component)
- Verified on Board A: derived SSID, captive portal, payment, wallet, wifistr publish

1 files changed, 13 insertions, 1 deletions

diff --git a/main/config.h b/main/config.h
index 2bcd400..8254a62 100644
--- a/main/config.h
+++ b/main/config.h
@@ -10,6 +10,7 @@
 #define TOLLGATE_MAX_MINT_URLS     3
 #define TOLLGATE_MAX_AP_SSID_LEN   32
 #define TOLLGATE_MAX_AP_PASS_LEN   64
+#define TOLLGATE_MAX_RELAYS        4
 
 typedef struct {
     char ssid[32];
@@ -22,11 +23,17 @@ typedef struct {
     int current_network;
     int max_retry;
 
+    char nsec[65];
+    char npub[65];
+
     char ap_ssid[TOLLGATE_MAX_AP_SSID_LEN];
     char ap_password[TOLLGATE_MAX_AP_PASS_LEN];
     uint8_t ap_channel;
     uint8_t ap_max_conn;
 
+    uint8_t sta_mac[6];
+    uint8_t ap_mac[6];
+
     esp_ip4_addr_t ap_ip;
     char ap_ip_str[16];
 
@@ -36,7 +43,12 @@ typedef struct {
     int step_size_ms;
     uint64_t persist_threshold_sats;
 
-    bool unique_derived;
+    char nostr_geohash[16];
+    char nostr_relays[TOLLGATE_MAX_RELAYS][128];
+    int nostr_relay_count;
+    int nostr_publish_interval_s;
+
+    bool identity_initialized;
 } tollgate_config_t;
 
 void tollgate_config_derive_unique(tollgate_config_t *cfg);