fix: make SSL verification opt-in via config, extend fix to all platforms

- Add DISABLE_SSL_VERIFY = False to base_config.py (default: verification on)
- Add tools/httpx_util.py with make_async_client() factory that reads the config
- Replace all httpx.AsyncClient() call sites across all platforms (bilibili,
  weibo, zhihu, xhs, douyin, kuaishou) and crawler_util with make_async_client()
- Extends SSL fix to previously missed platforms: xhs, douyin, kuaishou

Users running behind an intercepting proxy can set DISABLE_SSL_VERIFY = True
in config/base_config.py. All other users retain certificate verification.

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

tools/httpx_util.py

@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*-
+import httpx
+import config
+
+
+def make_async_client(**kwargs) -> httpx.AsyncClient:
+    """Create an httpx.AsyncClient with project-wide defaults.
+
+    Reads DISABLE_SSL_VERIFY from config (default False).
+    Set DISABLE_SSL_VERIFY = True in config/base_config.py only when running
+    behind an intercepting proxy (corporate gateway, Burp, mitmproxy, etc.).
+    """
+    kwargs.setdefault("verify", not getattr(config, "DISABLE_SSL_VERIFY", False))
+    return httpx.AsyncClient(**kwargs)