[TASK-276] Add unsubscribe_partition to python bindings

[fresh-borzoni]

Summary

closes #276

• Add unsubscribe_partition method to python bindings

[fresh-borzoni]

@luoyuxia @leekeiabstraction PTAL 🙏

[Copilot]

Pull request overview

Adds the missing unsubscribe_partition API to the Python bindings so Python users can mirror the unsubscribe functionality already available in the C++ and Rust clients.

Changes:

• Add LogScanner.unsubscribe_partition(partition_id, bucket_id) to the PyO3 bindings.
• Update Python type stubs (.pyi) to include the new method.
• Extend the Python example to demonstrate unsubscribing from a partition and reading remaining partitions.

Reviewed changes

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

File	Description
bindings/python/src/table.rs	Exposes unsubscribe_partition on the Python LogScanner, dispatching to either record or batch scanner implementation.
bindings/python/fluss/init.pyi	Adds the unsubscribe_partition method to Python type hints/stubs.
bindings/python/example/example.py	Demonstrates unsubscribing from a partition and reading remaining data via to_arrow().

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[luoyuxia]

@fresh-borzoni Thanks. LGTM!