style: fix badge centering over flags, plain theme toggle icon

- badgeRow now uses same gap (10px) as matchRow for exact alignment
- Theme toggle: removed button box, plain icon like admin gear
- Both icons use text-secondary color, consistent style

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/MatchCard.module.css

@@ -21,21 +21,24 @@
     inset 0 1px 0 rgba(255,255,255,0.07) !important;
 }
 
-/* Badge row — same flex proportions as matchRow so badges align over flags */
+/* Badge row — mirrors matchRow layout for centered alignment */
 .badgeRow {
   display: flex;
   align-items: center;
-  margin-bottom: 8px;
+  gap: 10px;
+  margin-bottom: 6px;
 }
 
 .badgeSlot {
   flex: 1;
   display: flex;
   justify-content: center;
+  min-width: 0;
 }
 
 .badgeSpacer {
-  min-width: 60px; /* matches scoreBox width */
+  min-width: 60px; /* matches scoreBox min-width */
+  flex-shrink: 0;
 }
 
 .status {