Replace deprecated document.execCommand with modern Clipboard API

- Replace document.execCommand('copy') with navigator.clipboard.writeText()
- Add fallback function for older browsers or non-secure contexts
- Fixes CSP eval blocking issues in modern browsers
- Improves clipboard functionality with better error handling

app/templates/main/user_tokens.html

@@ -390,12 +390,34 @@ function extendToken(tokenId, tokenName) {
 
 function copyToken() {
     const tokenInput = document.getElementById('newTokenValue');
-    tokenInput.select();
-    tokenInput.setSelectionRange(0, 99999); // For mobile devices
+    const tokenValue = tokenInput.value;
     
+    // Use modern Clipboard API if available
+    if (navigator.clipboard && window.isSecureContext) {
+        navigator.clipboard.writeText(tokenValue).then(() => {
+            showAlert('Token copied to clipboard!', 'success');
+        }).catch(err => {
+            console.error('Failed to copy token:', err);
+            fallbackCopyToken(tokenInput);
+        });
+    } else {
+        // Fallback for older browsers or non-secure contexts
+        fallbackCopyToken(tokenInput);
+    }
+}
+
+function fallbackCopyToken(tokenInput) {
     try {
-        document.execCommand('copy');
-        showAlert('Token copied to clipboard!', 'success');
+        tokenInput.select();
+        tokenInput.setSelectionRange(0, 99999); // For mobile devices
+        
+        // Use the deprecated execCommand as fallback
+        const successful = document.execCommand('copy');
+        if (successful) {
+            showAlert('Token copied to clipboard!', 'success');
+        } else {
+            showAlert('Failed to copy token. Please copy manually.', 'warning');
+        }
     } catch (err) {
         console.error('Failed to copy token:', err);
         showAlert('Failed to copy token. Please copy manually.', 'warning');