Fix mypy strict type checking errors

[yan]

Summary

• Fixed all mypy --strict errors without using cast()
• Uses runtime validation for better type safety

Changes

utils.py

• Use explicit float variable to avoid int/float type conflict

github_client.py

• Add type parameters to dict (dict[str, Any])
• Use isinstance() for runtime type checking in pagination
• Add explicit type annotation for JSON response

collector.py

• Add _parse_datetime_required() for non-optional datetime fields
• Returns datetime directly, raises ValueError if None
• Better error messages with field names

main.py

• Fix dict[str, any] to dict[str, Any]
• Add Any import from typing

All fixes use runtime validation instead of cast() for type safety.

Testing

• ✅ mypy --strict passes with no errors
• ✅ All existing tests still pass

🤖 Generated with Claude Code