style: convert var to const in sparkline toggle block (#16)

public/js/players.js

@@ -529,23 +529,23 @@ function closeAddPlayerModal(event) {
 
 // ── Sparkline toggle ───────────────────────────────
 document.addEventListener('DOMContentLoaded', function() {
-    var SPARKLINE_KEY = 'ratingtracker.sparklines';
+    const SPARKLINE_KEY = 'ratingtracker.sparklines';
 
     function syncSparklineButtons(state) {
-        var btns = document.querySelectorAll('#trendchart-toggle, #trendchart-toggle-mobile');
+        const btns = document.querySelectorAll('#trendchart-toggle, #trendchart-toggle-mobile');
         btns.forEach(function(b) {
             b.setAttribute('aria-pressed', state === 'on' ? 'true' : 'false');
         });
     }
 
-    var state = localStorage.getItem(SPARKLINE_KEY) || 'on';
+    const state = localStorage.getItem(SPARKLINE_KEY) || 'on';
     document.body.dataset.sparklines = state;
     syncSparklineButtons(state);
 
     document.body.addEventListener('click', function(e) {
-        var target = e.target.closest('#trendchart-toggle, #trendchart-toggle-mobile');
+        const target = e.target.closest('#trendchart-toggle, #trendchart-toggle-mobile');
         if (!target) return;
-        var next = document.body.dataset.sparklines === 'on' ? 'off' : 'on';
+        const next = document.body.dataset.sparklines === 'on' ? 'off' : 'on';
         document.body.dataset.sparklines = next;
         localStorage.setItem(SPARKLINE_KEY, next);
         syncSparklineButtons(next);
@@ -553,7 +553,7 @@ document.addEventListener('DOMContentLoaded', function() {
 
     // Re-sync after HTMX table swap (mobile button is inside the swapped partial)
     document.body.addEventListener('htmx:afterSwap', function(event) {
-        var target = event.detail.target;
+        const target = event.detail.target;
         if (target.id === 'ratings-table') {
             syncSparklineButtons(document.body.dataset.sparklines || 'on');
         }