[W1] Migrate packaging and development to uv

[Claudio9701]

Outcome

UrbanPy has one PEP 621 project definition, direct dependencies, a reproducible uv environment, and verified release artifacts.

Parent tasks

• choose Python support and build/version source via ADR
• replace setup.py and monolithic pinned requirements
• add pyproject.toml, uv.lock, dependency groups, and honest extras
• remove eager imports and import-time HDX configuration
• build and clean-install test wheel and sdist

Acceptance

A fresh checkout can sync, test, build, and install through documented uv commands on the supported matrix.

Plan: PR #61

[Claudio9701]

Implementation task opened: #73 (PEP 621 + uv foundation). The implementation PR will be stacked on #61.