Fix Google Charts not rendering with Turbolinks

Removed $(document).ready() wrapper inside google.load callback which
was preventing charts from rendering when page loaded via Turbolinks.

Changes:
- Remove document.ready wrapper (DOM already ready with Turbolinks)
- Add check for element existence before drawing chart
- Add guard to verify google.load exists before calling
- Create separate initializeChart function for cleaner callback

This ensures charts render properly on Turbolinks page loads where
the DOM is already ready when the script executes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/views/performance/index.html.erb

@@ -120,15 +120,22 @@ function makeActive(){
   $('li[id="performance"]').addClass('active');
 };
 
-// Load Google Charts and set callback
-google.load("visualization", "1", {
-  packages: ["corechart"],
-  callback: function() {
-    $(document).ready(function () {
+function initializeChart() {
+  // Check if element exists before drawing
+  if (document.getElementById('line_chart')) {
     drawChart2();
-      makeActive();
-    });
   }
-});
+  makeActive();
+}
+
+// Load Google Charts and set callback
+if (typeof google !== 'undefined' && google.load) {
+  google.load("visualization", "1", {
+    packages: ["corechart"],
+    callback: initializeChart
+  });
+} else {
+  console.error('Google JSAPI not loaded');
+}
 
 </script>