style: stärkerer Glossy-Effekt auf Flag-Boxen im Light Mode

Glanz-Overlay auf 55% angehoben, inset-Highlight und Border ergänzt
für MatchCard flagBox, TipModal flagLarge und pickerBtn.

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

frontend/src/components/MatchCard.module.css

@@ -107,8 +107,10 @@
   border-radius: 13px;
   background: var(--surface-high);
   box-shadow:
-    0 4px 12px rgba(0,0,0,0.3),
-    inset 0 1px 0 rgba(255,255,255,0.12);
+    var(--shadow-card),
+    inset 0 1px 0 rgba(255,255,255,0.55),
+    inset 0 -1px 0 rgba(0,0,0,0.06);
+  border: 1px solid var(--border-subtle);
   display: flex;
   align-items: center;
   justify-content: center;
@@ -121,8 +123,8 @@
   content: '';
   position: absolute;
   top: 0; left: 0; right: 0;
-  height: 50%;
-  background: linear-gradient(180deg, rgba(255,255,255,0.08) 0%, transparent 100%);
+  height: 55%;
+  background: linear-gradient(180deg, rgba(255,255,255,0.55) 0%, rgba(255,255,255,0.0) 100%);
   pointer-events: none;
   z-index: 1;
 }