improve signed reads, crypto hardening, and scraper transport

app/services/x_poster.py

@@ -33,7 +33,6 @@ import urllib.parse
 from datetime import datetime, timezone
 from typing import Optional
 
-import httpx
 from sqlalchemy import select
 
 from app.config import settings
@@ -146,8 +145,8 @@ async def _post_tweet(text: str, reply_to: Optional[str] = None) -> Optional[str
         "Content-Type": "application/json",
     }
     try:
-        async with httpx.AsyncClient(timeout=10) as client:
-            resp = await client.post(TWEET_URL, json=payload, headers=headers)
+        from app.services.http_client import get_client
+        resp = await get_client().post(TWEET_URL, json=payload, headers=headers, timeout=10)
         if resp.status_code in (200, 201):
             _record_sent()
             tid = resp.json().get("data", {}).get("id")