Fix PostHog transport in Cloudflare Workers

[yaacovcorcos]

Summary

• keep PostHog credentials scoped to the configured origin by handling redirects manually instead of following them
• avoid Cloudflare treating redirect: error as a failed subrequest before the response can be classified
• test that redirect responses are rejected as HTTP failures without being followed

Production evidence

The staged synthetic event was accepted into D1 but the current Worker recorded repeated network failures before receiving a PostHog response. This changes only the transport redirect mode; timeouts, bounded responses, origin scoping, retries, and HTTP rejection remain intact.

Qualification

• full website/Worker check suite passes
• 137 tests pass, 1 skipped
• site and Pages Functions builds pass

After merge, deploy the exact merge commit and repeat the isolated ingest/export/deletion proof.

[cloudflare-workers-and-pages]

Deploying scientfactory-website with    Cloudflare Pages

Latest commit:	2d41370
Status:	✅  Deploy successful!
Preview URL:	https://1cdf0f72.scientfactory-website.pages.dev
Branch Preview URL:	https://codex-analytics-transport-20.scientfactory-website.pages.dev

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