Adds the ability to apply provider search results to parts directly
from the bulk import step 2 page without navigating to individual
part edit forms. Includes per-result Quick Apply buttons and an
Apply All button for batch operations.
- Add BulkSearchResponseDTO, FieldMappingDTO for type safety
- Use composition instead of inheritance in BulkSearchResultDTO
- Remove unnecessary BulkSearchRequestDTO
- Fix N+1 queries and API error handling
- Fix Add Mapping button functionality