Rewrite maifetch in modern C++20

[Errordog2]

/claim #1

Fixes #1.

This is a modern C++20 rewrite for the maintainer's latest direction in #1 (comment).

What changed:

• Replaces the Go module with a C++20 CMake project.
• Adds a small maifetch_core library plus the CLI entrypoint.
• Uses libcurl for authenticated MaiTea API requests instead of shelling out to curl.
• Preserves the config precedence: CLI > environment > config file > defaults.
• Supports both original MAIFETCH_* env vars and the documented MAITEA_* aliases.
• Parses MaiTea profile/recent-play API responses and renders the profile summary/recent score output.
• Keeps ANSI truecolor formatting with --no-color for plain terminals.
• Adds focused tests for config precedence, env config-file selection, JSON parsing, and output formatting.
• Adds GitHub Actions CI for CMake configure/build/ctest on Ubuntu.

Validation performed locally:

• git diff --check
• Confirmed there are no remaining Go/Rust build instructions or helper-command leftovers in the rewritten tree.

I could not run the C++ build locally in this Windows environment because cmake, g++, clang++, and cl are not installed here. The PR includes CI with libcurl4-openssl-dev so GitHub can provide the authoritative build/test signal.

[Errordog2]

Validation update: the fork CI for this exact head passed successfully.

• Head: 34739c893e4295b05d2e31bc6875674868066d9a
• Workflow run: https://github.com/Errordog2/maifetch/actions/runs/27284772150
• Job: build-test completed successfully: https://github.com/Errordog2/maifetch/actions/runs/27284772150/job/80588824680

That run installs libcurl4-openssl-dev, configures with CMake, builds the C++20 target, and runs ctest --output-on-failure.

[Errordog2]

Validation update after expanding the C++20 API wrapper coverage:

• New head: 01b783d189a2f38c64ad7f59b88a52a434daaca7
• Added C++ wrapper coverage for tracks, scores, all plays/all scores, and status parsing/client methods, plus focused tests for those response shapes.
• Fork CI passed again: https://github.com/Errordog2/maifetch/actions/runs/27286515756
• Successful job: https://github.com/Errordog2/maifetch/actions/runs/27286515756/job/80595129058

The CI run installs libcurl4-openssl-dev, configures with CMake, builds the C++20 project, and runs ctest --output-on-failure.

[Errordog2]

Validation update after tightening the configurable API base URL support:

• New head: bf07bd9652ec7521d9723d742591ee1548e5a85c
• Added baseUrl JSON config support so --base-url, MAIFETCH_BASE_URL / MAITEA_BASE_URL, and config files cover the same API-base override surface.
• Updated README/help text for the documented API base URL option.
• Expanded config-priority tests for config-file, environment, and CLI base URL precedence.
• git diff --check passes locally.
• Fork CI passed CMake configure/build/ctest for this head: https://github.com/Errordog2/maifetch/actions/runs/27289370318