fix: date node now applies the format field

[sjoerdvink99]

What and why

The Date node offers ISO / Unix / Custom format options in the UI but the backend never reads the format config field. It always returns the raw string regardless of what the user selects.

How

Read format from config in execute. For "Unix", parse the value as RFC 3339 and emit seconds since epoch. ISO and Custom pass through unchanged.

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