Update test environment to fix integration tests with nginx 1.30

[clue]

This changeset updates the integration tests for two HTTP edge-case behaviors introduced when the nginx:stable-alpine image rolled forward to nginx 1.30. Both are expected interactions with how nginx now proxies to upstream and handles CONNECT, not changes in Framework X behavior, and the tests cover them through the suite's existing per-server skip mechanism, the same way it already handles other server-specific differences.

The 1.30 stable line picks up two changes from the nginx 1.29.x mainline. nginx 1.29.7 made HTTP/1.1 with keep-alive to upstream servers the default (nginx/nginx#1080, previously HTTP/1.0), so a Host-less HTTP/1.0 request now reaches the backend as HTTP/1.1, where a Host header is required. nginx 1.29.3 reworked CONNECT handling (nginx/nginx#935), so it now rejects proxied CONNECT requests with 405 Not Allowed rather than 400 Bad Request. Framework X handles both correctly, and a new assertion covers the HTTP/1.1 Host requirement explicitly.

Builds on top of #3, #46 and others

[Copilot]

Pull request overview

This PR adjusts the integration test suite to account for behavior changes observed when running Framework X behind newer nginx:stable-alpine (nginx 1.30), particularly around Host-less requests reaching upstream and proxied CONNECT handling.

Changes:

• Added an explicit assertion that Host-less requests should be rejected (400) (with a skip for the PHP development server behavior).
• Updated existing Host/UA/Accept header test with a new skip to tolerate nginx 1.29.7+ upstream behavior changes.
• Updated proxy CONNECT rejection test to skip nginx 1.30+ returning 405 instead of 400, plus a minor comment wording tweak.

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