feat: add CategoryImportController for bulk JSON import and export of categories

- Implemented export functionality to retrieve all rows from specified category tables.
- Developed import functionality with strict validation and referential integrity checks.
- Added error handling for various import scenarios including invalid formats and duplicate entries.
- Introduced tests for import functionality to ensure correct behavior and validation.

docs/api/location.md

@@ -247,3 +247,10 @@ Legacy endpoint that proxies to the new endpoints.
 
 > ⚠️ Response is **triple-nested**: `data?.data?.data ?? []`  
 > Note: `categorys` (not `categories`) is intentional — legacy route name.
+
+---
+
+## Bulk import / export
+
+Full-table JSON export and strict wipe+replace import for this category live under
+`/api/v1/admin/categories/{bundle}/{export|import}` — see [category-import.md](category-import.md).