fix(api): enable utoipa-swagger-ui reqwest feature for Windows cross-compile

[jacquesh82]

Summary

The release pipeline failed on x86_64-pc-windows-gnu because utoipa-swagger-ui 7.1.0's build.rs has a host-vs-target cfg mismatch when cross-compiling.

Symptom: thread 'main' panicked at .../utoipa-swagger-ui-7.1.0/build.rs:183:81: called Result::unwrap() on an Err value: Os { code: 2, kind: NotFound, message: "No such file or directory" }

Root cause: The build.rs has:
```rust
if reqwest_feature.is_ok() || CARGO_CFG_TARGET_OS == "windows" {
#[cfg(any(feature = "reqwest", target_os = "windows"))]
{ download_file_reqwest(...) }
Ok(())
} else { /* curl */ }
```
When cross-compiling from Linux to Windows, the runtime branch picks the windows path, but the inner #[cfg(target_os = "windows")] is evaluated against the host (Linux) at build-script compile time, so the inner block is excluded. The function returns Ok(()) without downloading, then later File::open panics.

Fix: Enable the reqwest feature on utoipa-swagger-ui. This makes the inner #[cfg(feature = "reqwest")] true regardless of host, so the download code is always compiled in.

Test plan

• After merge, re-tag (or move) v0.1.0-rc1 to re-trigger the release pipeline.
• Verify Windows native build succeeds and produces jot-windows-x86_64.exe, jot-server-windows-x86_64.exe, jot-mcp-windows-x86_64.exe.
• Linux/macOS builds should keep working unchanged.

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