fix(devtools): preserve Rozenite Metro frontend URLs

[DjDeveloperr]

Summary

• Keep Metro-served /rozenite/... DevTools frontend URLs instead of forcing them onto SimDeck’s bundled frontend
• Preserve the proxied ws socket parameter while retaining Rozenite’s injected runtime and plugin asset routes
• Leave the embedded rn_fusebox.html fallback behavior unchanged for plain React Native DevTools targets

Testing

• Added Rust unit coverage for Rozenite relative URLs, absolute Rozenite URLs, and the existing embedded frontend path
• cargo fmt --manifest-path server/Cargo.toml --check
• cargo test --manifest-path server/Cargo.toml

closes #44