Add chunked_filter for batch predicates - #491

Add chunked_filter(src, size, key=None) to filter an iterable using a predicate that handles batches, such as a database or API lookup. The helper preserves item order and identity, reads input one chunk at a time, and checks that the predicate returns one truth value per item.

This follows the feature discussion in #344 and the naming, error-message, and documentation feedback on the closed #346. It includes a batch-lookup doctest, an API documentation entry, and tests for lazy consumption, partial final chunks, generator predicates, invalid inputs, and predicate errors.

Fixes #344.

Validation: 103 iterutils tests/doctests passed; the complete suite passed with 689 tests/doctests on Windows with Python 3.12.14. git diff --check passed.

AI-assisted implementation, independently reviewed by a second coding agent.