fix/test: resolve schema type bug and complete API test TODOs

• Fix schemas.py: name field type was 'integer', corrected to 'string'
• Complete test_pet_schema: was failing due to schema bug
• Extend test_find_by_status_200: added all statuses, response code,
  status assertion, and per-object schema validation
• Implement test_get_by_id_404: parametrized with edge cases
• Implement test_patch_order_by_id: fixture, schema validation,
  status code and message assertions
• Add Order schema to schemas.py for store test validation
• Add test_patch_order_not_found for 404 coverage