feat(new-game): default Break rule and selected styling

- Default Break rule to 'winnerbreak' in BreakRuleStep
- Ensure selected quick-pick button styling matches Race To buttons
- Simplify Weiter button since rule is always defined

Fixes #30

src/components/NewGame.module.css

@@ -293,6 +293,13 @@
     color: white;
     box-shadow: var(--shadow-md);
 }
+/* Match selected styling for quick pick buttons used in BreakRuleStep */
+.quick-pick-btn.selected {
+    background: var(--color-primary);
+    border-color: var(--color-primary);
+    color: white;
+    box-shadow: var(--shadow-md);
+}
 .custom-race-to {
     display: flex;
     gap: var(--space-md);