Task 440: Deduplicate AU_KM Constant

Status: DONE

Summary

AU_KM = 149_597_870.7 is exported from kestrel.ts but several files define local copies or use the literal directly. Replace with imports from the single source of truth.

Files to Change

1. ephemeris.ts — local AU_KM, import from kestrel
2. orbital-3d-analysis.ts — local AU_KM, import from kestrel
3. timeline-analysis.ts — local AU_KM + 5 inline literals, import from kestrel
4. templates.ts — browser JS var KM_PER_AU = 149597870.7, interpolate