fix: support cache TTL configuration

[Lovlace777]

Summary

• Load CACHE_TTL from the runtime environment so cache expiration can be configured.
• Document the cache TTL and on-demand refresh behavior in the README.
• Add tests for configured and invalid CACHE_TTL values.

Validation

• python -m pytest tests/test_caching.py -> passed, 10 tests
• python -m pytest -> passed, 32 tests
• python -m pylint src/ --rcfile=.pylintrc -> passed, 10.00/10
• git diff --check -> passed

Notes

• Fixes Fix documentation typos and consistency issues #9.
• The default cache TTL remains 10 seconds unless CACHE_TTL is set.
• No compatibility impact is expected; this only enables the documented runtime override.

[rawbytedev]

Nice, Thanks for the help