Preserve timezone offsets in temporal values

[skhe]

Changes

• Preserve offsets when binding timezone-aware Python time and datetime values, or offset-bearing text.
• Return timezone offsets from DM TIME WITH TIME ZONE and TIMESTAMP WITH TIME ZONE columns.
• Add real-DM regression cases for aware Python values and text inputs, comparing instants after server timezone normalization.
• Record the local five-version regression result.

Verification

• Python 3.9, 3.10, 3.11, 3.12, 3.13: 112 real-DM tests passed per version on local OrbStack DM8 ARM.
• go test ./... passed.
• git diff --check passed.

Complex types and special connection environments remain tracked in the broader roadmap; this PR covers timezone values.