chore: add Claude.md file

[davidgamez]

Summary:

This pull request adds a new CLAUDE.md file to the repository, providing detailed guidance for using Claude Code (claude.ai/code) with this project. The document outlines the project's architecture, code generation workflow, ground rules, and common development commands, ensuring contributors understand how to interact with the codebase without introducing errors or breaking changes.

Documentation and contributor guidance:

• Added CLAUDE.md with an overview of the project structure, including the API, Cloud Functions, and database components, as well as infrastructure and integration test organization.
• Defined strict ground rules for contributions, emphasizing the importance of not committing or pushing changes without review and maintaining backward compatibility for public APIs and database schemas.
• Documented the code generation workflow, specifying which files are generated, how to regenerate them, and which scripts to use, to prevent manual edits to generated code.
• Listed common commands for setup, development, testing, and code generation to streamline onboarding and daily workflows.
• Provided architecture notes for both the API and Cloud Functions, including error handling conventions, integration test setup, and database migration processes.

Expected behavior:

Testing tips:

Provide tips, procedures and sample files on how to test the feature.
Testers are invited to follow the tips AND to try anything they deem relevant outside the bounds of the testing tips.

Please make sure these boxes are checked before submitting your pull request - thanks!

• Run the unit tests with ./scripts/api-tests.sh to make sure you didn't break anything
• Add or update any needed documentation to the repo
• Format the title like "feat: [new feature short description]". Title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
• Include screenshot(s) showing how this pull request works and fixes the issue(s)