Initial public release for deathbycaptcha-api-client-cpp.

Added

• Initial public release of this repository, aligned with the 4.7.x client family.
• Official C++20 DeathByCaptcha API client repository and project layout.
• dbc::HttpClient — HTTPS REST client using libcurl.
• dbc::SocketClient — TCP socket client (cleartext, faster responses).
• Abstract dbc::Client base class with shared polling logic.
• dbc::User and dbc::Captcha data models.
• dbc::AccessDeniedException and dbc::ServiceOverloadException exception types.
• Support for all 21 CAPTCHA types (type IDs 0–25).
• Polling schedule [1,1,2,3,2,2,3,2,2] then fixed 3 s intervals.
• Multiplatform support: Linux, Windows (MSVC / MinGW), macOS.
• CMake build system with CMakePresets.json (default, release, coverage, integration, examples).
• Unit test suite using GoogleTest + GoogleMock (>= 80 % line coverage target).
• Integration test suite (skips gracefully when credentials are absent).
• GitHub Actions workflows: unit tests, coverage (self-hosted badge), API integration, publish.
• 22 example programs covering all CAPTCHA types.
• MIT license, RESPONSIBLE_USE.md, and full README.md documentation.