fix: HTTP node now forwards headers input to the request

[sjoerdvink99]

What and why

The HTTP node declares a headers: Dict[String, String] input port but never reads it. Any headers wired in are silently dropped.

How

Read the headers input port in execute and forward each key-value pair into a reqwest::HeaderMap. Also switch from reqwest::Client::new() on every call to the shared ctx.http_client.

Linked issue

X

Type of change

• Bug fix
• New feature
• New node
• Language change (parser, type system, executor)
• Dashboard change
• Docs
• Refactor
• Other:

Checklist

• cargo build, cargo test, and cargo clippy pass.
• pnpm -C dashboard check passes (if frontend changed).
• New code has tests. Bug fixes have a regression test.
• No unrelated formatting churn.
• No commented-out code.
• No TODO or FIXME without a linked issue.
• If this is a node, backend and frontend port names/types match, and I built a tiny project that uses it end to end.
• If this is a language change, I opened an issue first and it was approved.

Screenshots / demo (if applicable)

X

Anything reviewers should pay extra attention to

X