feat(cyper): proxy support

[Berrysoft]

No description provided.

[Copilot]

Pull request overview

Adds first-class proxy support to the cyper HTTP client, including forward proxies, CONNECT tunneling for HTTPS, optional SOCKS support, and related integration tests.

Changes:

• Introduces cyper::proxy module with Proxy/NoProxy configuration and matching logic (including env/system proxy support).
• Updates client/connector/stream plumbing to route connections via matched proxies, including CONNECT tunneling and proxy auth handling.
• Adds comprehensive proxy integration tests (forward proxy, auth, CONNECT behavior, multiple proxies, no-proxy bypass).

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
cyper/src/proxy.rs	New proxy configuration/matching layer (Proxy, NoProxy, matchers, auth/headers helpers).
cyper/src/client.rs	ClientBuilder proxy configuration + request-time injection of proxy auth/custom headers.
cyper/src/connector.rs	Proxy-aware connector: chooses between direct, forward-proxy, CONNECT tunnel, and SOCKS paths.
cyper/src/stream.rs	Refactors HttpStream to carry proxy/H2 flags, adds wrapping/splitting support for proxy + tunneled flows.
cyper-core/src/stream.rs	Adds futures_util::AsyncRead/AsyncWrite impls to support splitting/wrapping strategy.
cyper/tests/proxy.rs	New integration tests covering forward proxy, auth, CONNECT error handling, no-proxy bypass, and proxy selection.
cyper/src/lib.rs	Exposes proxy module publicly and adds Error::Proxy.
cyper/src/nyquest/mod.rs	Enables use_default_proxy behavior by toggling proxy usage instead of erroring.
cyper/src/into_url.rs	Extends IntoUrl with as_str() to support proxy URL parsing convenience.
cyper/src/backend.rs	Switches TLS cfg gating to the new tls cfg alias.
cyper/build.rs	Adds cfg_aliases build script for tls cfg alias.
cyper/Cargo.toml	Enables hyper-util proxy support, adds cfg_aliases build-dep, introduces socks feature flag.
Cargo.toml	Adds cfg_aliases to workspace dependencies.

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