Initial dstalk project: core DLL + CLI + BearSSL TLS

- Core DLL: AI API client (DeepSeek/OpenAI compatible), HTTP(S) via Boost.Beast
- BearSSL vendored as TLS backend (MIT license, replacing OpenSSL)
- CLI frontend with ANSI colors, /help /model /file /save /load commands
- WinHTTP alternative HTTP client for Windows
- GPLv3 license with linking exception
- Build: CMake + Ninja + Clang, dependencies via Conan2

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

CMakeLists.txt

@@ -0,0 +1,12 @@
+cmake_minimum_required(VERSION 3.21)
+project(dstalk VERSION 0.1.0 LANGUAGES C CXX)
+
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+add_subdirectory(dstalk-core)
+add_subdirectory(dstalk-cli)
+# add_subdirectory(dstalk-gui)  # 等 SDL3 Conan 包可用后启用
+add_subdirectory(tests)