fix: preserve redirect URLs with async capture host prefixes

[nickita-khylkouski]

💡 Motivation and Context

When the configured capture host contains a path prefix, passing relative redirect paths through an HTTPX client can reapply or retain that prefix incorrectly. Resolve each redirect against the current absolute URL, enforce the original origin, and pass absolute URLs through the redirect chain.

💚 How did you test it?

• Full test suite: 2,502 passed, 15 skipped, 38 subtests passed
• Full mypy check: 230 source files, no issues
• Import smoke test and package build
• Added 307/308 coverage for absolute, root-relative, relative, and query-only redirects with prefixed hosts

The repository-wide Ruff command currently reports existing formatting and legacy-lint findings in untouched files; the modified Python files pass formatting.

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran sampo add to generate a changeset file

An equivalent patch changeset is included at .sampo/changesets/async-capture-redirect-path-prefix.md.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

The contributor directed the scope and redirect behavior. Codex helped inspect the repository, apply the bounded change, and run the repository checks; same-origin enforcement remains in place and fragments are not forwarded.

[marandaneto]

thanks @nickita-khylkouski