fix(reporting): identify account facts HTTP client

[Pigbibi]

Summary

Set a fixed, truthful service User-Agent (QSL-IBKR-AccountFacts/1.0) on the normal account-facts publisher and the isolated empty-body diagnostic. Add assertions on both actual request objects. Only two files, five added lines.

Evidence and validation

• Existing approved cloud environment, unauthenticated GET to the same endpoint: default Python client returned HTTP 403 / Cloudflare 1010; changing only User-Agent to this service identity returned application HTTP 404 / JSON not_found.
• 29 targeted tests passed; Ruff and git diff --check passed.
• The cloud GET comparison establishes the client-identity correction, not authenticated POST or funds-sync success.

Scope

User approved publication/adoption of this correction and one further fixed empty-body diagnostic via the existing isolated workflow. URL, token, body, 15-second timeout, no retry/redirect, 15-minute report freshness and all account guards are unchanged. No Cloudflare security configuration, credential update, broker sampling or real funds/report replay is authorized here.