fix(api): сравнение — одна строка на клинику с показательной ценой

Проверено end-to-end на реальной БД: 8871 позиций, 73.9% автонормализации,
живое сравнение цен по клиникам во фронте.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

api/main.py

@@ -66,13 +66,30 @@ def list_services(specialty: str | None = None, q: str | None = None, limit: int
 @app.get("/services/{service_id}/partners", response_model=list[PriceOut],
          summary="Кто оказывает услугу и по какой цене")
 def service_partners(service_id: str):
+    """Одна строка на клинику с показательной ценой (резидент или минимальный тариф)."""
     sql = """SELECT pi.partner_id, p.name AS partner_name, pi.price_resident, pi.price_nonresident,
                     pi.prices, pi.effective_date
              FROM price_item pi JOIN partner p ON pi.partner_id = p.partner_id
-             WHERE pi.service_id = ? AND pi.is_active = 1
+             WHERE pi.service_id = ? AND pi.is_active = 1"""
-             ORDER BY COALESCE(pi.price_resident, pi.price_nonresident)"""
+    best: dict[str, PriceOut] = {}
     with db() as conn:
-        return [_price_out(r) for r in conn.execute(sql, [service_id])]
+        for r in conn.execute(sql, [service_id]):
+            prices = json.loads(r["prices"] or "{}")
+            display = r["price_resident"] or (min(prices.values()) if prices else None)
+            current = best.get(r["partner_id"])
+            if current is None or (
+                display is not None
+                and (current.price_resident_kzt is None or display < current.price_resident_kzt)
+            ):
+                best[r["partner_id"]] = PriceOut(
+                    partner_id=r["partner_id"],
+                    partner_name=r["partner_name"],
+                    price_resident_kzt=display,
+                    price_nonresident_kzt=r["price_nonresident"],
+                    prices=prices,
+                    effective_date=r["effective_date"],
+                )
+    return sorted(best.values(), key=lambda x: x.price_resident_kzt or float("inf"))
 
 
 @app.get("/partners", response_model=list[PartnerOut], summary="Партнёры")