fix(security): guard remaining preflighted HTTP fetches

Several platform fetch paths called is_safe_url before constructing ordinary httpx clients, leaving a second DNS lookup at connection time. This preserved the rebinding window for Slack batch images, Feishu documents, Telegram URL-photo fallback, and WeCom remote media.

Route each path through create_ssrf_safe_async_client and the shared redirect guard so direct connections validate and dial vetted IPs while configured proxies remain an explicit trusted egress boundary. Add per-path regressions that change DNS from public at preflight to metadata at connect time.

The Skills Hub provenance fixture intentionally serves content over loopback. Opt that test-scoped server into private-address access so it keeps exercising the real HTTP transport without weakening production blocking.

Related #8033

Co-authored-by: teknium1 <127238744+teknium1@users.noreply.github.com>

plugins/platforms/feishu/adapter.py

@@ -3446,13 +3446,17 @@ class FeishuAdapter(BasePlatformAdapter):
         default_ext: str,
         preferred_name: str,
     ) -> tuple[str, str]:
-        from tools.url_safety import is_safe_url
+        from gateway.platforms.base import _ssrf_redirect_guard
+        from tools.url_safety import create_ssrf_safe_async_client, is_safe_url
+
         if not is_safe_url(file_url):
             raise ValueError(f"Blocked unsafe URL (SSRF protection): {file_url[:80]}")
 
-        import httpx
-
-        async with httpx.AsyncClient(timeout=30.0, follow_redirects=True) as client:
+        async with create_ssrf_safe_async_client(
+            timeout=30.0,
+            follow_redirects=True,
+            event_hooks={"response": [_ssrf_redirect_guard]},
+        ) as client:
             response = await client.get(
                 file_url,
                 headers={