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>

dstalk-core/thirdparty/bearssl/CMakeLists.txt

@@ -0,0 +1,43 @@
+# BearSSL static library (vendored, MIT license)
+# All .c files compiled as a single translation unit for best optimization
+
+add_library(bearssl STATIC)
+
+target_include_directories(bearssl
+    PUBLIC inc
+    PRIVATE src
+)
+
+# Collect all C source files
+file(GLOB_RECURSE BEARSSL_SOURCES "src/*.c")
+target_sources(bearssl PRIVATE ${BEARSSL_SOURCES})
+
+# x86_64 Windows optimizations
+if(WIN32 AND CMAKE_SIZEOF_VOID_P EQUAL 8)
+    target_compile_definitions(bearssl PRIVATE
+        BR_64
+        BR_INT128
+        BR_LE_UNALIGNED
+        BR_USE_WIN32_RAND
+        BR_USE_WIN32_TIME
+    )
+    # AES-NI and SSE2 are auto-detected by BearSSL on x86
+    if(CMAKE_C_COMPILER_ID MATCHES "Clang|GNU")
+        target_compile_options(bearssl PRIVATE -maes -msse2)
+    endif()
+elseif(UNIX)
+    target_compile_definitions(bearssl PRIVATE
+        BR_USE_URANDOM
+        BR_USE_UNIX_TIME
+    )
+    if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+        target_compile_definitions(bearssl PRIVATE BR_64 BR_INT128 BR_LE_UNALIGNED)
+    endif()
+endif()
+
+# Suppress warnings for vendored code
+if(MSVC)
+    target_compile_options(bearssl PRIVATE /W0)
+else()
+    target_compile_options(bearssl PRIVATE -w)
+endif()