fix: extend make_async_client to proxy provider and IP pool

Migrate remaining httpx.AsyncClient call sites in proxy/ package to
use make_async_client(), completing the DISABLE_SSL_VERIFY coverage
across all outbound HTTP requests in the project.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

proxy/proxy_ip_pool.py

@@ -26,6 +26,7 @@ from typing import Dict, List
 
 import httpx
 from tenacity import retry, stop_after_attempt, wait_fixed
+from tools.httpx_util import make_async_client
 
 import config
 from proxy.providers import (
@@ -81,7 +82,7 @@ class ProxyIpPool:
             else:
                 proxy_url = f"http://{proxy.ip}:{proxy.port}"
 
-            async with httpx.AsyncClient(proxy=proxy_url) as client:
+            async with make_async_client(proxy=proxy_url) as client:
                 response = await client.get(self.valid_ip_url)
             if response.status_code == 200:
                 return True