Extract planetary data into _data.py and add Wikidata refresh script

CHANGELOG.md

@@ -5,6 +5,18 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.3.0] - 2026-04-21
+
+### Added
+
+- `scripts/refresh_data.py` — fetches rotation periods, orbital periods, and discovery/contact dates from Wikidata SPARQL and regenerates `src/planetarytime/_data.py`; supports `--dry-run`; not part of the distributed package
+
+### Changed
+
+- Planetary and moon data extracted into `src/planetarytime/_data.py` (`PLANET_ROWS`, `MOON_ROWS`) — single source of truth for all numerical constants
+- `body.py`, `moon.py`, `epoch.py` now derive their data dictionaries from `_data.py` instead of hardcoding values inline
+- `README.md` — updated usage examples with current output values, added Exceptions section, added Refreshing data section
+
 ## [1.2.0] - 2026-04-16
 
 ### Added