This pull request refactors how test dependencies are managed for different backends (MongoDB, Redis, Postgres/SQL) by standardizing requirements file naming and updating the CI workflow accordingly. The changes improve clarity, maintainability, and consistency across documentation and automation scripts.

Test dependency management improvements:

• Renamed backend-specific requirements files in tests/ to requirements_mongodb.txt, requirements_redis.txt, and requirements_postgres.txt, and updated their contents to include a reference to requirements.txt for shared dependencies. [1] [2] [3]
• Updated the CI workflow in .github/workflows/ci-test.yml to install backend-specific test dependencies using the new requirements file names, and consolidated dependency installation steps for clarity. [1] [2] [3] [4] [5]

Documentation updates:

• Updated references to backend-specific requirements files in AGENTS.md, CLAUDE.md, and scripts/README-local-testing.md to use the new standardized file names. [1] [2] [3]