fix(object-chart): restore fixed eyepiece orientation baseline

[mrosseel]

Summary

• restore the upstream/ADR 0003 fixed 180° + solved-roll baseline for POSS and Gaia
• keep optical reflections represented by flip/flop after rotation
• centralize the shared transform so the image, chart, and live extent overlay cannot drift
• add first-principles North/East regression coverage across five rolls, all flip/flop combinations, and zero/nonzero obstruction

The object_images refactor accidentally made the 180° baseline conditional on central obstruction. Central obstruction does not determine image parity, and this made POSS and Gaia rotate together incorrectly for unobstructed or missing telescope configurations.

Validation

• 98 relevant tests passed
• Ruff format/check passed