feat(mining): Bitcoin mining-for-bandwidth payment system

New modules:
- mining_payment.c/h: hashprice calc (nbits->difficulty->sat/GH/s/day),
  share validation, client stats, allotment conversion (ms + bytes)
- stratum_client.c/h: SV1 upstream pool connection (subscribe/authorize/submit)
- stratum_proxy.c/h: Local SV1 TCP server for downstream miners, job broadcast
- sw_miner.c/h: Software SHA256d miner (ESP32 CPU fallback)
- asic_miner.c/h: ASIC detection stub (BM1366/BM1368 SPI)

Config:
- config.h/c: mining_payout_mode_t enum (auto/pool/upstream/proxy_only),
  stratum pool settings, mining port, hashprice override, sandbox mint access
- Defaults fill nostr_seed_relays (8/8) and nostr_relays (4/4) with fast relays

Integration into existing modules:
- session.h/c: payment_method_t enum (CASHU/MINING/BYTES)
- firewall.h/c: firewall_set_mining_port(), firewall_set_sandbox_mint_access()
- tollgate_api.c: GET /mining/job, POST /mining/share, GET /mining/stats
- tollgate_client.h/c: TG_CLIENT_MINING state, mining discovery tag parsing
- tollgate_main.c: mining init in start_services(), stratum_client_tick() in loop
- captive_portal.c: tabbed Cashu/Mine UI with live hashrate polling

Unit tests (69 new assertions across 4 suites):
- test_mining_payment (23 tests): nbits->difficulty, hashprice, client stats, allotment
- test_stratum_proxy (21 tests): job set/get, stats, type validation
- test_session_payment_method (12 tests): PAYMENT_METHOD enum, bytes/cashu methods
- test_tollgate_client_mining (20 tests): mining tag parsing, discovery struct
- test_firewall_sandbox (16 tests): client grant/revoke, max clients, setters

Enhanced test stubs:
- BaseType_t/pdPASS in freertos/task.h
- lwip: sockets.h, etharp.h, prot/ip.h, prot/ip4.h, prot/tcp.h, netif.h
- dns_server.h, esp_wifi_ap_get_sta_list.h

Build fixes:
- cvm_server.c: replace esp_timer_get_time() with xTaskGetTickCount(),
  fix process_relay_message() 3-arg call to 2-arg, add WS keepalive ping
- stratum_proxy.c: widen task_name buffer 16->20
- sw_miner.c: add missing #include esp_random.h
- nucula_src: save_proofs() moved to public in wallet.hpp

Nostr relay updates:
- nostr_seed_relays: +relay.anzenkodo.workers.dev, +nostr.koning-degraaf.nl,
  +knostr.neutrine.com, +nostr.einundzwanzig.space (8/8 slots)
- nostr_relays: +relay.anzenkodo.workers.dev, +nostr.koning-degraaf.nl (4/4 slots)

Squash-merge of feature/mining-payment (5 commits: c75230e..9d98ba1)

1 files changed, 31 insertions, 1 deletions

diff --git a/main/tollgate_main.c b/main/tollgate_main.c
index 33e5b90..561fc3f 100644
--- a/main/tollgate_main.c
+++ b/main/tollgate_main.c
@@ -31,6 +31,11 @@
 #include "sync_manager.h"
 #include "beacon_price.h"
 #include "market.h"
+#include "stratum_client.h"
+#include "stratum_proxy.h"
+#include "sw_miner.h"
+#include "asic_miner.h"
+#include "mining_payment.h"
 
 #define MAX_STA_RETRY 5
 static const char *TAG = "tollgate_main";
@@ -190,7 +195,6 @@ static void start_services(void)
     session_manager_init();
 
     const tollgate_config_t *cfg = tollgate_config_get();
-
     mint_health_init(cfg->accepted_mints, cfg->accepted_mint_count);
     mint_health_start();
 
@@ -199,6 +203,11 @@ static void start_services(void)
     } else {
         nucula_wallet_init(cfg->mint_url);
     }
+
+    if (cfg->mining_enabled) {
+        firewall_set_mining_port(cfg->mining_port);
+        firewall_set_sandbox_mint_access(cfg->mining_sandbox_mint_access);
+    }
     lightning_payout_init(&cfg->payout);
 
     dns_server_start(ap_ip_info.ip, upstream_dns);
@@ -223,6 +232,26 @@ static void start_services(void)
         cvm_server_start();
     }
 
+    if (cfg2->mining_enabled) {
+        ESP_LOGI(TAG, "Mining subsystem enabled, initializing...");
+        mining_payment_init();
+        stratum_client_init();
+        stratum_proxy_init(cfg2->mining_port);
+
+        if (cfg2->mining_payout_mode != MINING_PAYOUT_UPSTREAM) {
+            stratum_client_start();
+        }
+
+        asic_miner_init();
+        if (asic_miner_is_present()) {
+            asic_miner_start();
+            ESP_LOGI(TAG, "ASIC miner started");
+        } else {
+            sw_miner_start();
+            ESP_LOGI(TAG, "Software miner started (no ASIC)");
+        }
+    }
+
     s_services_running = true;
     if (s_services_mutex) xSemaphoreGive(s_services_mutex);
     ESP_LOGI(TAG, "=== TollGate services started ===");
@@ -392,5 +421,6 @@ void app_main(void)
         tollgate_client_tick();
         lightning_payout_tick();
         market_tick();
+        stratum_client_tick();
     }
 }