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, 6 insertions, 3 deletions

diff --git a/main/CMakeLists.txt b/main/CMakeLists.txt
index 2eef030..df69283 100644
--- a/main/CMakeLists.txt
+++ b/main/CMakeLists.txt
@@ -6,9 +6,12 @@ idf_component_register(SRCS "tollgate_main.c"
                             "cashu.c"
                             "session.c"
                             "tollgate_api.c"
-                             "wallet.c"
-                            "wallet_persist.c"
-                    INCLUDE_DIRS "." "${IDF_PATH}/components/lwip/include/apps"
+                            "identity.c"
+                            "nostr_event.c"
+                            "geohash.c"
+                            "wifistr.c"
+                    INCLUDE_DIRS "."
                     REQUIRES esp_wifi esp_event esp_netif nvs_flash esp_http_server
                              lwip json esp_http_client mbedtls esp-tls log spiffs
+                             nucula_lib secp256k1
                     PRIV_REQUIRES esp-tls)