improve signed reads, crypto hardening, and scraper transport

app/services/hl_price_feed.py

@@ -31,7 +31,6 @@ import time
 from datetime import datetime, timezone
 from typing import Optional
 
-import httpx
 
 from app.services.price_store import price_store
 from app.ws.manager import manager
@@ -96,10 +95,10 @@ async def _tick() -> None:
     """Single price fetch + dispatch cycle for all HL_PRICE_ASSETS."""
     now_ms = int(time.time() * 1000)
 
-    async with httpx.AsyncClient(timeout=4.0) as c:
-        r = await c.post(HL_API_URL, json={"type": "allMids"})
-        r.raise_for_status()
-        mids: dict = r.json()  # {"BTC": "74541.0", "HYPE": "13.5", …}
+    from app.services.http_client import get_client
+    r = await get_client().post(HL_API_URL, json={"type": "allMids"}, timeout=4.0)
+    r.raise_for_status()
+    mids: dict = r.json()  # {"BTC": "74541.0", "HYPE": "13.5", …}
 
     # Feed is alive the moment we successfully fetch mids, even if a specific
     # asset is momentarily absent from the response.