chore: add explicit type definitions to consumer arrays and datetime utils

[mishrak5j]

💡 Motivation and Context

This PR improves static analysis verification and type safety across utils.py and consumer.py.

• posthog/utils.py: Added concrete type annotations to foundational datetime utility methods (is_naive, total_seconds, guess_timezone, remove_trailing_slash) to resolve implicit inference gaps and improve IDE auto-completion.
• posthog/consumer.py: Explicitly typed the background worker's event collection array (items: list[Any] = []) to pass strict static variance checking.

These adjustments eliminate mypy type check errors and improve overall SDK maintainability without introducing runtime performance changes.

💚 How did you test it?

• Validated via local static type analysis: Checked cleanly using mypy posthog/utils.py.
• Verified via localized formatting suite: All hooks executed cleanly via pre-commit run.
• Confirmed runtime stability: Successfully ran the full tracking verification engine with pytest (982 passed).

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR adds/strengthens type hints in utility and consumer code, improving static analysis and readability.

Changes:

• Added datetime/timedelta and return/arg type annotations in posthog/utils.py.
• Added Any import and typed items in Consumer.next().

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
posthog/utils.py	Adds type annotations for datetime helpers and string utility.
posthog/consumer.py	Adds typing for the upload batch list in next().

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[greptile-apps]

_{Reviews (1): Last reviewed commit: "chore: add explicit type definitions to ..." | Re-trigger Greptile}

[turnipdabeets]

LGTM, thanks @mishrak5j