feat(mining): integrate mining subsystem into existing modules

- CMakeLists.txt: add 6 mining sources + tcp_transport dependency
- config.h/c: mining_payout_mode_t enum, mining config fields, JSON parsing
- tollgate_main.c: mining init in start_services(), stratum_client_tick in main loop
- tollgate_api.c: GET /mining/job, POST /mining/share, GET /mining/stats endpoints
- session.h/c: payment_method_t enum (CASHU/MINING/BYTES)
- firewall.h/c: sandbox allowlist for mining port + mint URLs
- tollgate_client.h/c: TG_CLIENT_MINING state, mining discovery tag parsing
- captive_portal.c: tabbed UI with Cashu/Mine tabs, live hashrate polling

1 files changed, 7 insertions, 0 deletions

diff --git a/main/session.h b/main/session.h
index 36fe722..d3a61bb 100644
--- a/main/session.h
+++ b/main/session.h
@@ -8,6 +8,12 @@
 #define SESSION_MAX_CLIENTS     10
 #define SESSION_MAX_MAC_LEN     18
 
+typedef enum {
+    PAYMENT_METHOD_CASHU,
+    PAYMENT_METHOD_MINING,
+    PAYMENT_METHOD_BYTES
+} payment_method_t;
+
 typedef struct {
     uint32_t client_ip;
     char mac[SESSION_MAX_MAC_LEN];
@@ -15,6 +21,7 @@ typedef struct {
     int64_t start_time_ms;
     uint64_t allotment_bytes;
     uint64_t bytes_consumed;
+    payment_method_t payment_method;
     bool active;
 } session_t;