fix(integrations): pin api_call to the SSRF-validated IP

[ashvinctrl]

Summary

execute_api_call (src/integrations.py) runs check_outbound_url on the target before making the request, but that guard only resolves the host to answer (ok, reason) — it hands back no address. The request right after it opened a plain httpx.AsyncClient(), which resolves the host again at connect time. A base_url host on a low TTL can pass the guard as a public IP and then flip to 169.254.169.254 for the connect, so the call lands on cloud metadata with the integration's stored auth headers attached. That's the DNS-rebinding TOCTOU in #5513.

The fix resolves once, remembers the IPs the guard actually validated, and pins the client's socket to that set through a small AnyIO-backed transport. SNI and the Host header still come from the URL, so TLS and vhost routing are unchanged; connect-time fallback stays inside the approved address set over one shared deadline. This is the same pinning the webhook sender (src/webhook_manager.py) and web-fetch (services/search/content.py) paths already do — api_call was the last outbound path that skipped it.

Target branch

• This PR targets dev, not main.

Linked Issue

Fixes #5513

Type of Change

• Bug fix (non-breaking — fixes a confirmed issue)

Checklist

• I searched open issues and open PRs — this is not a duplicate.
• This PR targets dev
• My changes are limited to the scope described above — no unrelated refactors or whitespace changes mixed in.
• I actually ran the app (docker compose up or uvicorn app:app) and verified the change works end-to-end. Type-checks and unit tests are not enough.

How to Test

1. python -m pytest tests/test_integration_api_call_ssrf.py tests/test_integrations_api_call_truncation.py — 21 pass. On dev (no pin), the 9 pin tests in the first file fail.
2. Rebinding proof: stand up two loopback servers on the same port, one on 127.0.0.1 (the address the guard validates) and one on 127.0.0.2 (a stand-in for the metadata host). Point the guard's resolver at 127.0.0.1 and monkeypatch the connect-time resolver (anyio._core._sockets.getaddrinfo) to return 127.0.0.2, then call execute_api_call on a bearer integration. On dev the request lands on 127.0.0.2 and the Authorization header leaks; with this PR it stays on 127.0.0.1.
3. Normal calls to a real integration still work — the pin only fixes the socket destination, not the hostname used for TLS/Host.