Add complete custom fields implementation and entry editing

- Add custom field CRUD in admin UI (create, read, update, delete)
- Display custom fields on frontend form with proper field types
- Save custom field values on form submission
- Display custom field columns in entries table (admin and public)
- Include custom field values in all export formats (CSV, PairGoTh, OpenGotha, McMahon)
- Add Edit button and form for entries
- Update entry handler to support editing with custom field values
- Add success/error notices for all admin actions

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

go-form-plugin/export/csv.php

@@ -10,16 +10,23 @@ $form_id = intval($_POST['value_one']);
 $form = go_form_get_form_by_id($form_id);
 $form_name = $form ? $form->name : 'Unknown Form';
 $entries = go_form_get_entries($form_id);
+$custom_fields = go_form_get_custom_fields($form_id);
 
 header('Content-Type: text/csv; charset=utf-8');
 header('Content-Disposition: attachment; filename="go-form-' . sanitize_title($form_name) . '-export.csv"');
 
 $output = fopen('php://output', 'w');
-fputcsv($output, ['ID', 'First Name', 'Last Name', 'Country', 'Club', 'Rank', 'Rating', 'EGD Number', 'Date Added']);
+
+// Build header row
+$header = ['ID', 'First Name', 'Last Name', 'Country', 'Club', 'Rank', 'Rating', 'EGD Number', 'Date Added'];
+foreach ($custom_fields as $field) {
+  $header[] = $field->field_name;
+}
+fputcsv($output, $header);
 
 foreach ($entries as $e) {
   global $ranks;
-  fputcsv($output, [
+  $row = [
     $e->id,
     $e->first_name,
     $e->last_name,
@@ -29,7 +36,15 @@ foreach ($entries as $e) {
     $e->rating,
     $e->egd_number,
     $e->created_at
-  ]);
+  ];
+  
+  // Add custom field values
+  foreach ($custom_fields as $field) {
+    $value = go_form_get_custom_value($e->id, $field->id);
+    $row[] = $value;
+  }
+  
+  fputcsv($output, $row);
 }
 
 fclose($output);