[TASK-252] Temporal Types CPP

[fresh-borzoni]

Summary

closes #252

• Add temporal type support (Date, Time, Timestamp, TimestampLtz) to C++ bindings — both write and read paths
• C++ wrapper types (Date, Time, Timestamp) with factory methods (FromYMD, FromHMS, FromTimePoint, etc.) and decomposition accessors
• Write path packs temporal values into existing FfiDatum fields (no struct changes)
• Read path uses Fluss table schema to disambiguate TimestampNtz vs TimestampLtz (Arrow loses this distinction)
• Pre-compute projected columns (aligned with Python bindings approach) so projection works correctly with temporal type disambiguation
• DatumType values 11–14 for temporal types (8–10 reserved for decimal PR)

[fresh-borzoni]

@luoyuxia @zhaohaidao
Appreciate your review here. PTAL 🙏

[Copilot]

Pull request overview

Adds end-to-end temporal type (Date/Time/Timestamp/TimestampLtz) support to the C++ bindings by introducing C++ wrapper types and extending the Rust<->C++ FFI conversions to correctly encode/decode temporal values, including LTZ vs NTZ disambiguation during reads (including projected scans).

Changes:

• Add temporal DatumType values and map them on the Rust FFI conversion paths (row->core and core->row).
• Disambiguate TimestampNtz vs TimestampLtz on the read path using the Fluss schema columns (and keep this correct under projection).
• Introduce C++ Date/Time/Timestamp wrapper types and extend the C++ example to exercise temporal writes/reads and projection.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
bindings/cpp/src/types.rs	Adds temporal datum types and packs/unpacks Arrow temporal arrays into existing FfiDatum fields; uses schema columns to distinguish NTZ vs LTZ.
bindings/cpp/src/lib.rs	Tracks projected columns in LogScanner and passes them into scan-record conversion to keep temporal disambiguation correct under projection.
bindings/cpp/src/table.cpp	Implements Date decomposition/factory functions used by the C++ API.
bindings/cpp/include/fluss.hpp	Adds C++ temporal wrapper types plus Datum/GenericRow helpers for temporal values.
bindings/cpp/examples/example.cpp	Extends example to write/read temporal columns and validate type behavior under full scan and projection.

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[fresh-borzoni]

added macro for correct time functions and out of bounds check

[zhaohaidao]

@fresh-borzoni Thanks for your pr. LGTM