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>

.gitignore

@@ -12,6 +12,10 @@ frontend/.vite/
 .env
 backend/.env
 
+# Import data — large binary files, not committed
+03-data/
+obstsorten.zip
+
 # macOS
 .DS_Store