REMAG v0.2.0

• release: bump version to 0.2.0
• refactor: remove HDBSCAN, use Leiden exclusively
• fix: correct embedding name mismatch in refinement
• refactor: remove unused refinement functions
• refactor: clean up unnecessary improvement comments
• docs: restructure installation
• add miniprot dependency and improve error handling
• perf: parallelize Leiden k-NN graph construction
• fix: cleanup build config and docs consistency
• add: generated version file
• fix: handle GPU import exceptions gracefully
• fix: remove GPU pip extras, add conda install docs
• refactor: move plotting to optional dependencies
  Full Changelog: v0.1.5...v0.2.0