Add test coverage checklist, report template, and stack matrix for ecommerce project

- Created a test coverage checklist to ensure comprehensive testing of backend and frontend components.
- Added a test report template to standardize reporting on test execution results and gaps.
- Introduced a test stack matrix to guide the selection of testing tools and frameworks for backend and frontend.
- Established a skill for repairing failing tests, including a failure triage checklist and a test repair template.
- Documented recommended MCP stack for ecommerce development with FastAPI and React/Next.js.
- Developed a detailed README outlining the project structure, agent capabilities, and recommended workflows.
- Compiled a comprehensive workflow guide detailing step-by-step commands for project setup, testing, and SEO implementation.

site-fullstack/.github/prompts/ecommerce-code-review.prompt.md

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+name: "Ecommerce Code Review"
+description: "Run a strict full-project code review using pyproject, package.json, and current versions to produce .ai/CODE-REVIEW.md with harsh findings and fixes."
+agent: "shop-fullstack-fastapi-react"
+Review the project strictly.
+
+Requirements for this run:
+- Inspect the actual project configuration first.
+- Respect configured Python quality tools such as mypy, ty, ruff, and deptry.
+- Review React code for readability, maintainability, and appropriate use of modern supported features.
+- Prefer findings over praise.
+- Create or update .ai/CODE-REVIEW.md.
+- Use current, version-appropriate guidance rather than outdated generic advice.