Backend Sprint 2+3: Health-Modul, Multi-Dog Tagebuch, Pillow, Migrations

- database.py: diary_dogs + walk_participant_dogs Tabellen, idempotente
  Migration für Health-Felder (charge_nr, kosten, diagnose, …), Backfill
- routes/health.py: vollständiges Health-Modul (war Stub), CRUD für
  Impfung/Entwurmung/Tierarzt/Medikament/Gewicht/Allergie/Dokument
- routes/diary.py: Multi-Dog n:m via diary_dogs (dog_ids in allen Endpoints)
- routes/dogs.py: Foto-Upload konvertiert HEIC/PNG/WebP → JPEG via Pillow
- routes/poison.py: Resolve mit Grundauswahl + Soft-Delete (geloest_von/at/grund)
- ki.py: health_summary() für KI-Gesundheitsbericht
- main.py: /favicon.ico Route
- requirements.txt: Pillow 11.2.1 + pillow-heif 0.22.0

backend/routes/dogs.py

@@ -113,13 +113,28 @@ async def upload_photo(
     if not dog:
         raise HTTPException(404, "Hund nicht gefunden.")
 
-    # Datei speichern
-    ext      = os.path.splitext(file.filename or "")[1] or ".jpg"
-    filename = f"dog_{dog_id}_{uuid.uuid4().hex[:8]}{ext}"
+    # Datei immer als JPEG speichern (HEIC/PNG/WebP → kompatibel für alle Browser)
+    import io
+    from PIL import Image
+    try:
+        import pillow_heif
+        pillow_heif.register_heif_opener()
+    except ImportError:
+        pass
+
+    content = await file.read()
+    try:
+        img = Image.open(io.BytesIO(content)).convert("RGB")
+        buf = io.BytesIO()
+        img.save(buf, format="JPEG", quality=90)
+        content = buf.getvalue()
+    except Exception:
+        pass  # Fallback: Originaldaten speichern
+
+    filename = f"dog_{dog_id}_{uuid.uuid4().hex[:8]}.jpg"
     path     = os.path.join(MEDIA_DIR, "dogs", filename)
     os.makedirs(os.path.dirname(path), exist_ok=True)
 
-    content = await file.read()
     with open(path, "wb") as f:
         f.write(content)