feat: import fruit DB from XML — scripts/import_fruits.py (story #03)

Adds a repeatable Python import script that populates fruits, fruit_synonyms,
and fruit_images from 03-data/obstsorten.xml and the three image directories.
Idempotent: deletes synonyms and images per fruit before re-inserting; upserts
fruit row by osdb_number. Reads DATABASE_URL from env.

- map_typ: 23 XML typ codes → 17-value fruit_type enum; aggregate types coerced
  with logged warning; typ='p' (2 entries) mapped to Pfirsiche
- parse_synonyms: comma-split with whitespace/newline strip, empty filter
- parse_date: YYYYMMDD → date, fallback None → DB default NOW()
- find_images: globs {id}_*_s0.* across einzelfruechte/blueten/baume dirs
- 42 unit tests (no DB required) cover all mapping, parsing, and glob logic
- Makefile test target extended to include Python test suite
- 03-data/ and obstsorten.zip added to .gitignore (large binary data)

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

Makefile

@@ -30,10 +30,11 @@ run-backend:
 run-frontend:
 	cd frontend && npm run dev
 
-## test: run all backend and frontend tests
+## test: run all backend, frontend, and script tests
 test:
 	cd backend && go test ./...
 	cd frontend && npm run test -- --run
+	cd scripts && python3 -m unittest import_fruits_test -v
 
 ## fmt: format all code
 fmt: