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, 31 insertions, 0 deletions

diff --git a/components/nucula_lib/nucula_wallet.h b/components/nucula_lib/nucula_wallet.h
new file mode 100644
index 0000000..64b7c24
--- /dev/null
+++ b/components/nucula_lib/nucula_wallet.h
@@ -0,0 +1,31 @@
+#ifndef NUCULA_WALLET_H
+#define NUCULA_WALLET_H
+
+#include "esp_err.h"
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+esp_err_t nucula_wallet_init(const char *mint_url);
+
+esp_err_t nucula_wallet_receive(const char *token_str);
+
+esp_err_t nucula_wallet_send(uint64_t amount_sat, char *token_out, size_t token_out_size);
+
+uint64_t nucula_wallet_balance(void);
+
+int nucula_wallet_proof_count(void);
+
+char *nucula_wallet_proofs_json(void);
+
+esp_err_t nucula_wallet_swap_all(void);
+
+void nucula_wallet_print_status(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif