fix: generate-bindings fails on Windows

## Summary
The generate-bindings script fails on Windows due to hardcoded bash invocation and the generate-bindings script treats windows as "Unsupported os".

### Error:
<3>WSL (9) ERROR: CreateProcessCommon:559: execvpe(/bin/bash) failed: No such file or directory
error: recipe `generate-bindings` failed on line 43 with exit code 1

### Proposed Solution
Refactor the generate-bindings recipe to conditionally execute native Cargo and UniFFI commands inside the native/ directory when running on Windows, while preserving the existing shell script execution for UNIX-based platforms.

Start with the generate-bindings recipe and reproduce the failure on Windows, then compare its hardcoded Bash invocation with the native/ directory workflow. Done means Windows runs the native Cargo and UniFFI commands while UNIX-based platforms retain the existing shell-script path, without the Unsupported os error.

Written by the indexing model from the issue text.