Fix executemany support

[BentsiLeviav]

hook.insert_rows(..., executemany=True) was raising AttributeError: 'tuple' object has no attribute 'keys' because clickhouse-connect's Cursor._try_bulk_insert expected dict rows, while DbApiHook.insert_rows always passes serialized tuples (PEP 249
sequences).

Fixed in clickhouse-connect 1.3.0 (released 2026-06-11). This PR bumps the minimum requirement to >=1.3.0 across pyproject.toml, README.rst, and docs/index.rst, and adds regression tests that exercise the real cursor with tuple rows.

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Claude code

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[koletzilla]

Looks good to me! :D