improve signed reads, crypto hardening, and scraper transport

app/api/prices.py

@@ -1,7 +1,6 @@
 import logging
 from typing import List
 
-import httpx
 from fastapi import APIRouter, HTTPException, Query, Request
 from fastapi.responses import Response
 
@@ -33,9 +32,9 @@ async def fetch_binance_candles(asset: str, tf: str, limit: int) -> List[Candle]
     symbol = SYMBOL_MAP[asset]
     interval = BINANCE_INTERVAL[tf]
     url = f"{settings.binance_rest_url}/api/v3/klines?symbol={symbol}&interval={interval}&limit={limit}"
-    async with httpx.AsyncClient(timeout=15) as client:
-        resp = await client.get(url)
-        resp.raise_for_status()
+    from app.services.http_client import get_client
+    resp = await get_client().get(url, timeout=15)
+    resp.raise_for_status()
     rows = resp.json()
     return [
         Candle(