fix: classification results empty and res.data access issues

Backend:
- Add GET /classifications/results endpoint with project/level/keyword filters
- Add column relationship to ClassificationResult model
- Fix test data generator to fetch column IDs from DB after bulk insert

Frontend:
- Fix request.ts interceptor to return full response body (keep total/pagination)
- Fix all pages to use res.data instead of res
- Add getClassificationResults API in classification.ts
- Implement fetchData in Classification.vue with proper filtering and pagination
- Fix same res.data issue in Category.vue, Metadata.vue, Project.vue, DataSource.vue, Dashboard.vue, Task.vue

backend/scripts/generate_test_data.py

@@ -417,7 +417,9 @@ print(f"  Created {len(projects)} projects")
 # ============================================================
 print("Generating classification results...")
 
-all_col_ids = [c.id for c in all_columns]
+# Re-fetch column IDs from DB since bulk_save_objects doesn't populate object IDs
+col_rows = db.query(DataColumn.id).all()
+all_col_ids = [c[0] for c in col_rows]
 random.shuffle(all_col_ids)
 
 result_batch = []