feat: create tollgate_core standalone C library + tollgate_esp IDF component

Phase 1-4: Extract core business logic into reusable library

tollgate_core/ — standalone C library (zero ESP-IDF deps):
  - tollgate_core.c — orchestrator (init, process_payment, process_share, tick)
  - tollgate_cashu.c — V3 token decode, checkstate via platform callback, allotment math
  - tollgate_session.c — session lifecycle state machine (create/find/revoke/extend)
  - tollgate_firewall.c — client allowlist, NAT filter, packet filter
  - tollgate_mining.c — hashprice, nbits→difficulty, shares-to-allotment, client stats

components/tollgate_esp/ — ESP-IDF component wrapper:
  - tollgate_esp_platform.c — implements tollgate_platform_t using ESP-IDF APIs
  - CMakeLists.txt — compiles tollgate_core + ESP wrapper, links to ESP-IDF
  - idf_component.yml — for IDF Component Registry

Platform interface (tollgate_platform.h):
  - Config access: price, step_size, mint_url, metric
  - Time: get_time_ms (via FreeRTOS ticks on ESP)
  - Logging: log_info/warn/error (via ESP_LOG on ESP)
  - Wallet: receive/send/balance (via nucula on ESP)
  - HTTP: http_post (via esp_http_client on ESP)
  - WiFi/MAC: mac_for_ip, napt_enable
  - Mining: stratum config, hashprice override

Build verification:
  - tollgate_core compiles standalone: cmake + make (gcc, host)
  - tollgate_esp + ESP-IDF full build: passes (idf.py build)
  - Unit tests: 22/22 pass (make test-unit)
  - No behavioral change to existing main/ code yet (Phase 5)

1 files changed, 65 insertions, 0 deletions

diff --git a/tollgate_core/include/tollgate_core.h b/tollgate_core/include/tollgate_core.h
new file mode 100644
index 0000000..fc20caa
--- /dev/null
+++ b/tollgate_core/include/tollgate_core.h
@@ -0,0 +1,65 @@
+#ifndef TOLLGATE_CORE_H
+#define TOLLGATE_CORE_H
+
+#include "tollgate_platform.h"
+#include <stdbool.h>
+#include <stdint.h>
+
+int tollgate_core_init(const tollgate_platform_t *platform, uint32_t ap_ip);
+void tollgate_core_tick(void);
+
+int tollgate_core_dns_start(uint32_t upstream_dns);
+void tollgate_core_dns_stop(void);
+
+int tollgate_core_process_payment(uint32_t client_ip, const char *token_str);
+int tollgate_core_process_share(uint32_t client_ip, const char *job_id,
+                                const char *nonce, const char *ntime, const char *version);
+
+void tollgate_core_client_connected(const uint8_t *mac, uint32_t client_ip);
+void tollgate_core_client_disconnected(const uint8_t *mac);
+
+bool tollgate_core_is_client_allowed(uint32_t client_ip);
+bool tollgate_core_is_dns_running(void);
+
+char *tollgate_core_get_status_json(void);
+char *tollgate_core_get_config_json(void);
+
+int tollgate_core_active_session_count(void);
+int tollgate_core_allowed_client_count(void);
+int tollgate_core_firewall_revoke_all(void);
+void tollgate_core_firewall_set_mining_port(uint16_t port);
+void tollgate_core_firewall_set_sandbox_mint_access(bool enable);
+
+bool tollgate_core_is_owner(uint32_t client_ip);
+bool tollgate_core_is_owner_connected(void);
+
+double tollgate_core_get_hashprice(void);
+void tollgate_core_set_nbits(uint32_t nbits);
+const void *tollgate_core_get_current_job(void);
+void tollgate_core_set_job(const void *job);
+
+int tollgate_core_stratum_client_start(void);
+void tollgate_core_stratum_client_stop(void);
+
+int tollgate_core_stratum_proxy_init(uint16_t port);
+void tollgate_core_stratum_proxy_get_stats(void *out);
+
+void tollgate_core_mining_init(void);
+
+void tollgate_core_beacon_start(void);
+
+void tollgate_core_market_init(void);
+void tollgate_core_market_on_scan_result(const void *ie_data, int ie_len,
+                                          const uint8_t *bssid, int rssi);
+
+const void *tollgate_core_get_sessions_array(void);
+int tollgate_core_get_sessions_array_size(void);
+void *tollgate_core_find_session_by_ip(uint32_t ip);
+void *tollgate_core_find_session_by_mac(const char *mac);
+void tollgate_core_session_extend(void *session, uint64_t additional_ms);
+int tollgate_core_session_add_bytes(uint32_t client_ip, uint64_t bytes);
+
+const tollgate_platform_t *tollgate_core_get_platform(void);
+uint32_t tollgate_core_get_ap_ip(void);
+
+#endif