test: add coverage for event parsing and deduplication

[w3lld1]

Description

I added focused pytest coverage for the shared event parsing and classification logic:

• region detection across all supported continents, including unknown-location rescue from event details
• deduplication behavior for same-series events in different cities and reworded duplicates
• ISO and month-name date parsing
• README parsing of escaped pipes

I also added a small development requirements file so the test runner can be installed independently of the fetcher dependencies.

Fixes #56

Type of Change

• New Event(s)
• New Fetcher
• Bug Fix
• New Feature
• Refactor/Cleanup

Checklist

• I have read the CONTRIBUTING.md guidelines.
• If I added a new Python script/fetcher, I have tested it locally to ensure it fetches events without crashing. (Not applicable; no fetcher was added.)
• I have not manually deleted past events (the automation handles this).
• I have not committed any API keys, client secrets, or .env files.
• My code follows the existing style of the project.

Validation

• python -m pytest test_aggregate.py tests -q — 16 passed
• python -m py_compile tests/test_config.py tests/test_parse_readme.py fetchers/config.py checks/parse_readme.py
• git diff --check

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.