feat: 集成大模型AI、重构构建系统并修复多项代码质量问题

- 构建系统：Makefile 迁移至 CMakeLists.txt，支持 cJSON 和 WinHTTP
- 项目结构：src/ 按功能拆分为 core/、gui/、network/、record/、llm/ 子目录
- 新功能：集成大模型 AI（WinHTTP + cJSON，兼容 OpenAI 协议），支持异步请求
- 渲染修复：IupDraw* 替换为 Windows GDI，修复画布黑屏问题
- 网络修复：ENet 初始化幂等化，实现真实 get_local_ip() (Winsock)
- 代码质量：删除死代码 (dfs/count_threats_in_direction)，修复头文件守卫，
  sprintf→snprintf 防溢出，strncpy 安全终止，GDI 资源泄漏修复

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

CMakeLists.txt

@@ -0,0 +1,87 @@
+cmake_minimum_required(VERSION 3.16)
+project(Gobang VERSION 9.0 LANGUAGES C)
+
+set(CMAKE_C_STANDARD 17)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+
+# === 输出目录：与原 Makefile 保持一致 ===
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/bin)
+
+# === 编译选项 ===
+add_compile_options(-Wall -Wextra -O2)
+add_compile_options(-finput-charset=UTF-8 -fexec-charset=UTF-8)
+
+# === ENet（从源码编译静态库）===
+set(ENET_DIR ${CMAKE_SOURCE_DIR}/libs/enet)
+add_library(enet STATIC
+    ${ENET_DIR}/callbacks.c
+    ${ENET_DIR}/compress.c
+    ${ENET_DIR}/host.c
+    ${ENET_DIR}/list.c
+    ${ENET_DIR}/packet.c
+    ${ENET_DIR}/peer.c
+    ${ENET_DIR}/protocol.c
+    ${ENET_DIR}/win32.c
+)
+target_include_directories(enet PUBLIC ${ENET_DIR}/include)
+
+# === IUP（预构建导入库）===
+set(IUP_DIR ${CMAKE_SOURCE_DIR}/libs/iup-3.31_Win64_dllw6_lib)
+add_library(iup SHARED IMPORTED)
+set_target_properties(iup PROPERTIES
+    IMPORTED_IMPLIB   ${IUP_DIR}/libiup.a
+    IMPORTED_LOCATION ${IUP_DIR}/iup.dll
+    INTERFACE_INCLUDE_DIRECTORIES ${IUP_DIR}/include
+)
+
+# === cJSON（JSON处理库）===
+add_library(cjson STATIC ${CMAKE_SOURCE_DIR}/libs/cJSON/cJSON.c)
+target_include_directories(cjson PUBLIC ${CMAKE_SOURCE_DIR}/libs/cJSON)
+
+# === 主可执行文件 ===
+add_executable(gobang_gui
+    src/core/main.c
+    src/core/globals.c
+    src/core/config.c
+    src/core/gobang.c
+    src/core/ai.c
+    src/network/network.c
+    src/record/record.c
+    src/gui/gui_core.c
+    src/gui/gui_game.c
+    src/gui/gui_menu.c
+    src/gui/gui_replay.c
+    src/llm/llm_ai.c
+)
+
+target_include_directories(gobang_gui PRIVATE ${CMAKE_SOURCE_DIR}/include)
+
+target_link_libraries(gobang_gui PRIVATE
+    enet
+    cjson
+    iup
+    winhttp
+    ws2_32
+    winmm
+    gdi32
+    comdlg32
+    comctl32
+    uuid
+    ole32
+)
+
+# === 构建后拷贝 iup.dll 到 bin/ ===
+add_custom_command(TARGET gobang_gui POST_BUILD
+    COMMAND ${CMAKE_COMMAND} -E copy_if_different
+        ${IUP_DIR}/iup.dll
+        $<TARGET_FILE_DIR:gobang_gui>
+    COMMENT "拷贝 iup.dll 到输出目录"
+)
+
+# === 快捷运行目标 ===
+add_custom_target(run
+    COMMAND gobang_gui
+    DEPENDS gobang_gui
+    WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}/bin
+    COMMENT "运行五子棋游戏"
+)