v0.2.1

Comets from JPL SBDB: apparition-specific elements for past dates

MPC CometEls only lists currently observable comets at current epochs;
images from past years need the elements of THAT apparition. The SBDB
query API exports every catalogued comet (4k) with per-apparition
epochs and perihelion times — C/2020 F3 (NEOWISE) propagated to its
famous 2020-07-13 appearance lands 2.7 arcmin from JPL Horizons, six
years in the past. CometEls remains the fallback for discoveries newer
than the SBDB sync.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>