Refactor keyword handling: Replace 'intent' with 'country' across backend and frontend

- Updated AutomationService to include estimated_word_count.
- Increased stage_1_batch_size from 20 to 50 in AutomationViewSet.
- Changed Keywords model to replace 'intent' property with 'country'.
- Adjusted ClusteringService to allow a maximum of 50 keywords for clustering.
- Modified admin and management commands to remove 'intent' and use 'country' instead.
- Updated serializers to reflect the change from 'intent' to 'country'.
- Adjusted views and filters to use 'country' instead of 'intent'.
- Updated frontend forms, filters, and pages to replace 'intent' with 'country'.
- Added migration to remove 'intent' field and add 'country' field to SeedKeyword model.

frontend/src/config/import-export.config.tsx

@@ -161,7 +161,7 @@ export function useImportExport(
             </p>
             {filename === 'keywords' && (
               <p className="text-xs text-gray-600 dark:text-gray-300 mt-2 p-2 bg-blue-50 dark:bg-blue-900/20 rounded border border-blue-200 dark:border-blue-800">
-                <strong>Expected columns:</strong> keyword, volume, difficulty, intent, status
+                <strong>Expected columns:</strong> keyword, volume, difficulty, country, status
               </p>
             )}
           </div>