Add TimeZone (geo)

[vhrcgcom]

Description

Implement TimeZone as a ValueObject in the geo module.

Spec: IANA timezone name (e.g. Europe/Prague)

Implementation checklist

• Create src/geo/timezone.rs
• Implement ValueObject trait
• Add #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
• Export from src/geo/mod.rs and prelude
• Unit tests: valid input · empty input · invalid format · normalisation
• Doc comment with # Example block
• Update status in ROADMAP.md from ⬜ to ✅

Implementation detail

Input / Output

	Type	Alias
Input	String	TimeZoneInput
Output	String	TimeZoneOutput

Normalization

Trim.

Validation

Must be a known IANA timezone name (e.g. "Europe/Prague", "America/New_York", "UTC"). Validate against a static list of accepted names embedded at compile time. Do not use an external runtime lookup — embed the list of ~600 canonical IANA names as a phf set or a sorted &[&str] with binary search.

Extra methods

None beyond the trait.

References

• ROADMAP.md
• CONTRIBUTING.md