fix: apply code-review findings to import_fruits script and tests

- find_images: verify exact fruit_id prefix (stem-parse before _s0.) to
  prevent cross-fruit image contamination (e.g. mitschurins steals
  mitschurins_fruchtbare images)
- DATA_DIR uses os.path.abspath to handle symlinks / relative invocation
- counts["images"] derived from IMAGE_DIRS constant, not hardcoded keys
- counts["warnings"] incremented on missing-id/name skip (was missing)
- UPSERT preserves existing comment (comment = fruits.comment, not NULL)
- Print summary and rollback moved inside try/except to avoid NameError
- Remove dead XML_PATH constant
- Tests: add tearDown to clean up tmpdir; fix vacuous _tn exclusion test
  to include positive-control _s0 file; add prefix-collision regression test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -6,6 +6,7 @@ A full-stack fruit-variety database (Go + Vue 3).
 
 - Users can view a "Hello, OSDB!" landing page that confirms the backend is reachable via the Vite proxy.
 - Users can create, view, edit, and delete fruit varieties, including managing synonyms and uploading images.
+- Administrators can bulk-import the legacy fruit database from XML using `scripts/import_fruits.py`.
 
 ## Quick Start