Add temporal and decimal type support to python row append() API

[fresh-borzoni]

Search before asking

• I searched in the issues and found nothing similar.

Description

The append() method currently only supports primitives. Add support for Date, Time, Timestamp, and Decimal types.
Implementation

1. /crates/fluss/src/record/arrow.rs:188-205 - Add Date32Builder, TimestampBuilder, Decimal128Builder
2. /crates/fluss/src/row/datum.rs:299-306 - Remove error, add append logic
3. /bindings/python/src/table.rs:404 - Add Python to Datum converters

Python types to support:

• datetime.date -> Date
• datetime.datetime -> Timestamp
• pd.Timestamp, np.datetime64 -> Timestamp
• Decimal -> Decimal

Willingness to contribute

• I'm willing to submit a PR!