Create comprehensive E2E tests for the base images management modal covering both happy paths and error scenarios.

Test Coverage:

Happy Path Tests (with real backend):
1. Add base image flow:

• Navigate to Results page
• Open "Manage images" dropdown
• Click "Base images" option
• Enter valid base image path (e.g., docker.io/library/ubuntu:22.04)
• Submit form and wait for scan completion
• Verify success alert shows with normalized name
• Verify image appears in table with correct "Added by" user

2. Remove base image flow:

• Open Base Images modal
• Click "Remove from list" on a base image
• Verify success alert appears
• Verify image removed from table
• Verify list refetches and updates

Error Scenarios (with mocked APIs):
3. Test all error types:

• INVALID_IMAGE_NAME - malformed image path
• NO_VALID_INTEGRATION - no registry integration
• SCAN_FAILED - scan error
• DUPLICATE_PATTERN - pattern already exists
• Verify appropriate error messages display
• Verify modal stays open for retry
• Verify form re-enables after error

Acceptance Criteria:

• All happy path tests pass with real backend
• All error scenarios covered with mocked responses
• Tests are stable and don't flake
• Retry behavior validated (modal stays open, form re-enables)