Ci build and static checks implementation

[dariopellegrino00]

Summary

Add CI job for:

• build check using cached docker image
• static checks using clang and cppcheck

[Copilot]

Pull Request Overview

This PR implements CI infrastructure to add automated build and static code analysis for the mod_openai_audio_stream project. The changes introduce GitHub Actions workflow for continuous integration with Docker-based builds and multiple static analysis tools.

• Adds CI workflow with build verification and static code analysis using clang and cppcheck
• Creates Docker-based CI environment with FreeSWITCH SDK and analysis tools
• Updates project documentation with CI badge and improved description

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
README.md	Adds CI badge and improves project description with better formatting and clarity
Dockerfile.ci	Multi-stage Docker build for creating FreeSWITCH SDK environment with static analysis tools
.github/workflows/checks.yml	GitHub Actions workflow implementing build checks and static analysis with clang-tidy and cppcheck

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