Prepare the project for 0.2.0 release

[prantogg]

Summary

Bump workspace version from 0.1.0 to 0.2.0 across all crates and update release documentation examples to reference 0.2.0.

Changes

• Cargo.toml: workspace version → 0.2.0
• spatialbench-arrow/Cargo.toml: crate version + spatialbench dep → 0.2.0
• spatialbench-cli/Cargo.toml: crate version + spatialbench and spatialbench-arrow deps → 0.2.0
• dev/release/README.md: update all example commands from 0.1.0 to 0.2.0, update post-release version bump example to 0.3.0

Not changed (intentionally)

• spatialbench/Cargo.toml — inherits version from workspace, no change needed
• .github/workflows/benchmark.yml HF_DATA_VERSION: v0.1.0 — refers to benchmark data version on HuggingFace, not the crate version

[paleolimbot]

Thank you!