Add client-side whitespace trimming for AR field names and labels

- Add form submit listener to trim field name and label inputs
- Provides immediate feedback to users before server-side validation
- Creates defense-in-depth approach with JS, route, and model layer trimming

src/app/templates/admin/ar_fields.html

@@ -111,6 +111,20 @@
 </div>
 
 <script>
+// Trim whitespace from field name and label on form submission
+document.getElementById('fieldForm').addEventListener('submit', function(e) {
+    var fieldNameInput = document.getElementById('fieldName');
+    var labelInput = document.getElementById('label');
+
+    // Trim whitespace from inputs before submission
+    if (fieldNameInput && !fieldNameInput.disabled) {
+        fieldNameInput.value = fieldNameInput.value.trim();
+    }
+    if (labelInput) {
+        labelInput.value = labelInput.value.trim();
+    }
+});
+
 function editField(button) {
     // Get data from button attributes
     var fieldData = {