Chair/Seat Rendering Polish Pass, Real Bathroom Door Sprite

A long chain of small, iterative fixes to chair and seat rendering: draw-order/occlusion fixes so a chair doesn't wrongly cover or get covered by the wrong neighbor, a south-seat position nudge (sitting position drifted slightly off-center relative to its table), chair sprite transparency fixed (an artifact showing through where it shouldn't), a chair/table alignment gap fixed, a texture seam fixed specifically on 2-top pairs, and a customer-drawn-over-their-own-seat ordering bug fixed. Also: the bathroom doorway gained real double-door artwork (the same doorway sprite system later reused for CHEF!'s kitchen door — see this file's own later entry on that), replacing a plain gap in the wall.