Feature: Sprint31 — 9 Features merged (Streak, Ausgaben, KI-Tierarzt, Rückrufe, Adoption, Vet+Befunde, Hundepass, Playdate, Rassenerkennung)

- Trainings-Streak: streak.py, DB training_streaks, Scheduler 19:00, Widget in welcome.js, Ping in uebungen.js
- Ausgaben-Tracker: expenses.py, expenses.js, DB expenses-Tabelle
- KI-Tierarztfragen: ki.py /tierarzt, health.js Button+Modal, DB ki_tierarzt_log
- Rückruf-Alarm: recalls.py, recalls.js, DB feed_recalls, Scheduler 08:00 RASFF
- Adoption: adoption.py, adoption.js, DB adoption_cache
- Tierarzt-Favorit + Befunde: tieraerzte.py /my-favorite+/favorite, health_docs.py, health.js, api.js, DB favorite_vets+health_documents
- Digitaler Hundepass: passport.py, dog-profile.js, main.py /pass/{token}, DB vaccinations+medications+dog_passport_meta+passport_shares, requirements.txt fpdf2
- Playdate-Matching: playdate.py, playdate.js, DB playdate_listings+playdate_requests
- Rassen-Erkennung: ki.py /rasse-erkennung (Claude Vision), dog-profile.js+wiki.js, CSS .rasse-result-card, DB ki_rasse_log

backend/routes/tieraerzte.py

@@ -63,15 +63,68 @@ def _fmt_opening_hours(raw: str | None) -> str | None:
     return result
 
 
+@router.get("/my-favorite")
+async def get_my_favorite(user=Depends(get_current_user)):
+    """Favoriten-Tierarzt des Users (oder null)."""
+    with db() as conn:
+        row = conn.execute(
+            """SELECT t.* FROM tieraerzte t
+               JOIN favorite_vets fv ON fv.vet_id = t.id
+               WHERE fv.user_id = ?
+               LIMIT 1""",
+            (user["id"],)
+        ).fetchone()
+    if not row:
+        return None
+    return dict(row)
+
+
+@router.post("/{vet_id}/favorite")
+async def toggle_favorite(vet_id: int, user=Depends(get_current_user)):
+    """Tierarzt als Favorit setzen oder entfernen (toggle). Gibt {is_favorite: bool} zurück."""
+    with db() as conn:
+        vet = conn.execute(
+            "SELECT id FROM tieraerzte WHERE id=?", (vet_id,)
+        ).fetchone()
+        if not vet:
+            raise HTTPException(404, "Tierarzt nicht gefunden.")
+
+        existing = conn.execute(
+            "SELECT 1 FROM favorite_vets WHERE user_id=? AND vet_id=?",
+            (user["id"], vet_id)
+        ).fetchone()
+
+        if existing:
+            conn.execute(
+                "DELETE FROM favorite_vets WHERE user_id=? AND vet_id=?",
+                (user["id"], vet_id)
+            )
+            return {"is_favorite": False}
+        else:
+            conn.execute(
+                "INSERT INTO favorite_vets (user_id, vet_id) VALUES (?, ?)",
+                (user["id"], vet_id)
+            )
+            return {"is_favorite": True}
+
+
 @router.get("")
 async def list_tieraerzte(user=Depends(get_current_user)):
-    """Alle Tierärzte des Users — aktive zuerst, dann inaktive."""
+    """Alle Tierärzte des Users — aktive zuerst, dann inaktive. Enthält is_favorite."""
     with db() as conn:
         rows = conn.execute(
             "SELECT * FROM tieraerzte WHERE user_id=? ORDER BY aktiv DESC, name",
             (user["id"],)
         ).fetchall()
-    return [dict(r) for r in rows]
+        favs = {r["vet_id"] for r in conn.execute(
+            "SELECT vet_id FROM favorite_vets WHERE user_id=?", (user["id"],)
+        ).fetchall()}
+    result = []
+    for r in rows:
+        d = dict(r)
+        d["is_favorite"] = r["id"] in favs
+        result.append(d)
+    return result
 
 
 @router.get("/osm-nearby")