Migrate HTTP client to cpp-httplib to simplify build process

[jiuker]

Background
Identified that the current HTTP client implementation involves a complicated build process. Suggested migrating to cpp-httplib as a better alternative.
Proposal
Replace the current HTTP client library with cpp-httplib.
Benefits

• Simplified Build Process: As a header-only library, cpp-httplib will significantly reduce build complexity and eliminate the cumbersome compilation steps we currently face.

Action Items

• Evaluate integration points for cpp-httplib
• Replace existing HTTP client implementation
• Update build scripts / CMakeLists.txt
• Verify all existing HTTP functionalities work as expected
• Update documentation if necessary

[jiuker]

Resolving this issue will also fix #227

[jiuker]

Resolved by #257 (merged in 2f3aefa). The HTTP client was migrated from curlpp to cpp-httplib (header-only, no libcurl): dependency resolution, build scripts and CMake were updated, and the full test suite passes across the CI matrix. The remaining action items (docs etc.) were covered by the PR.