fix(court): show near-side mascot backs and mirror racket hand by facing

[haritabh17]

What

• P3/P4 (near side) mascots now face away from the viewer: same figure rendered without face and front-only details (eyes, muzzle, beak, belly patch), so their backs read on screen. Ears, jersey band, capes, tails and racket stay; the number chip stays visible and reads as the jersey-back number. Applies only to mascot looks — classic round markers are unchanged.
• Racket hand now respects facing: for front-facing players (P1/P2) the right hand shows on the screen's left and vice versa; for back-facing players (P3/P4) the right hand shows on the screen's right.

How

• mascots.tsx: ArtProps gains an optional back flag; each mascot's head/body skips face and front-only elements when set. MascotView exposes it as facingAway.
• PlayerMarker.tsx: new facingAway prop; mirror rule is flipped = facingAway ? isLeftHanded : !isLeftHanded (raw art holds the racket on the screen's right).
• BadmintonCourt.tsx: team-2 markers pass facingAway.

3D pins are plain dots, and the Customize sheet tiles are neutral front-facing previews — both untouched.

Testing

• tsc --noEmit, eslint clean; jest 85/85 pass.