Cleaned up UI + replaced json config files with toml + fixed kafka local runs.

[s3rius]

This pull request introduces several improvements and refactorings to the FastAPI template project, focusing on better configuration management, modernization of the project generation hooks, and enhancements to the documentation and environment setup. The most significant changes include switching from JSON to TOML for manifest files, improving the post-generation project setup, updating Docker documentation for consistency, and enhancing the .env and test instructions for new features and services.

Configuration and manifest improvements:

• Migrated conditional and replaceable resource manifests from JSON to TOML (conditional_files.json → conditional_files.toml, replaceable_files.json → replaceable_files.toml) for improved readability and maintainability. Updated all related code in post_gen_project.py to use TOML parsing with tomllib instead of JSON. [1] [2] [3]

Project generation and hook enhancements:

• Refactored the post_gen_project.py hook to use Path objects for file operations, added a reusable run_cmd function for better subprocess error handling and output, and enhanced the init_repo function with improved logging, error handling, and repeated pre-commit runs for robustness. [1] [2]
• Changed the generate_project function in __main__.py to use default_config=True for cookiecutter, simplifying the configuration process.

Documentation and Docker usage improvements:

• Updated all Docker-related commands in README.md to use the modern docker compose syntax instead of the deprecated docker-compose, and clarified instructions for running auxiliary services and tests, making the documentation more accurate and user-friendly. [1] [2] [3]
• Improved OpenTelemetry documentation to reference Grafana and the correct UI endpoints.

Environment and feature support:

• Enhanced the .env template to support Kafka by adding a conditional environment variable when Kafka is enabled.
• Updated test instructions to account for the presence of auxiliary services (Redis, RabbitMQ, Kafka, NATS, database) and provided a unified Docker Compose command for starting them as needed.

Code style and cleanup:

• Minor code style improvements, such as import formatting in __main__.py.