feat: upgrade tollgate_core to full version with mining + stratum

Replace skeleton tollgate_core (9 files, 7 callbacks) with full version
from feature/miner-integration (13 files, 22 callbacks):

New modules:
- tollgate_core_mining.c/h — mining payment session management
- tollgate_core_stratum_proxy.c/h — SV1 stratum proxy

Updated:
- tollgate_core.h — extern C guards, 5 new mining API functions
- tollgate_platform.h — extern C guards, 22 platform callbacks (was 7)
- tollgate_core_firewall.c — conditional CONFIG_LWIP_IPV4_NAPT
- CMakeLists.txt — mining + stratum source files

Also adds MINER_INTEGRATION_PLAN.md from the feature branch.

1 files changed, 2 insertions, 0 deletions

diff --git a/components/tollgate_core/CMakeLists.txt b/components/tollgate_core/CMakeLists.txt
index fc6b6f1..1b7d84a 100644
--- a/components/tollgate_core/CMakeLists.txt
+++ b/components/tollgate_core/CMakeLists.txt
@@ -4,6 +4,8 @@ idf_component_register(
          "src/tollgate_core_dns.c"
          "src/tollgate_core_firewall.c"
          "src/tollgate_core_session.c"
+         "src/tollgate_core_mining.c"
+         "src/tollgate_core_stratum_proxy.c"
     INCLUDE_DIRS "include" "src"
     REQUIRES lwip json esp_http_client mbedtls log esp_netif
     PRIV_REQUIRES esp_wifi)