fix: restore 1:1 image ratio — remove max-height constraint

The max-height broke the square aspect ratio needed for object coordinate
overlays. Layout fix in App.jsx already ensures correct heights; the
image constraint was unnecessary.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/PairCards.css

@@ -83,8 +83,6 @@
   position: relative;
   width: 100%;
   aspect-ratio: 1 / 1;
-  /* Bild nie höher als ~40% des Viewport, damit die Karte komplett sichtbar ist */
-  max-height: 40dvh;
   overflow: hidden;
   cursor: default;
   background: #1a1a1a;