Refactor for future maintainability

[Teqed]

This pull request is part of the work to make it easier for people to read and contribute to FediFetcher.

To achieve this, we needed to:

• Split find_posts.py into multiple files, as it is currently approaching 1,000 LOC.
• Enforce code style by Ruff configuration of 'ALL'.
• Refactor functions to improve reusability and DRY principle.
• Add additional docstring documentation.
• Revise variable and function names to improve clarity and adherence to naming conventions.
• Enhance logging and debugging capabilities by implementing a structured logging framework and adjustable logging levels by configuration file or command line argument.
• Improve error handling and exception messages.
• Address warnings from static code analysis tools.
• Update dependencies to their latest versions.

Todo:

• Introduce unit tests.
• Introduce integration tests.
• Update the project's README with the latest changes and contribution guidelines.
• Make use of Mastodon.py.
• Perform benchmarking or profiling to measure the performance.
• Optimize performance.

[Teqed]