Prune pre-epoch day and hour partitions conservatively

[osipovartem]

Summary

• Project negative timestamp day predicates against both floor-based and legacy truncation-toward-zero partition IDs.
• Project negative hour equality only when both IDs fit in i32; leave negative hour ranges unpruned because wrapped IDs break monotonicity.
• Compute negative day/hour literal IDs with checked integer division, avoiding the extreme-date scalar conversion path.
• Test actual manifest pruning masks, including an i64::MIN day literal and an out-of-range hour literal.

Verification

• cargo +1.99.0 test -p datafusion_iceberg --lib: 113 passed, 2 ignored.
• cargo +1.99.0 clippy -p datafusion_iceberg --all-targets: passed with existing warnings; one new warning was fixed afterward.
• cargo +1.99.0 fmt --all -- --check and git diff --check: passed.
• Independent read-only review: approved after two correctness fixes.

The positive-timestamp and NULL fast paths are unchanged. Rustice integration test and dependency pin are being validated in a separate branch.