feat(scripts): add build-rust.sh for cross-platform Rust native library builds

Add new build script for Rust native libraries:

- Builds dataset_hash and queue_index crates via cargo

- Cross-platform support: Linux (.so), macOS (.dylib), Windows (.dll)

- Outputs to bin/native/ for consistency with C++ native libs

- Error handling for missing cargo installation

scripts/build/build-rust.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+# Builds Rust native libraries for cross-platform
+# Run on Ubuntu self-hosted runner or macOS
+
+set -euo pipefail
+
+echo "=== Building Rust Native Libraries ==="
+
+# Check for Rust
+if ! command -v cargo &> /dev/null; then
+    echo "Error: cargo not found. Please install Rust: https://rustup.rs/"
+    exit 1
+fi
+
+# Build native libraries
+cd native_rust
+echo "Building with cargo..."
+cargo build --release
+cd ..
+
+# Package libs for current platform
+mkdir -p bin/native
+if [[ "$OSTYPE" == "linux-gnu"* ]]; then
+    cp native_rust/target/release/lib*.so bin/native/ 2>/dev/null || true
+    echo "✓ Rust libraries built for Linux"
+elif [[ "$OSTYPE" == "darwin"* ]]; then
+    cp native_rust/target/release/lib*.dylib bin/native/ 2>/dev/null || true
+    echo "✓ Rust libraries built for macOS"
+else
+    cp native_rust/target/release/lib*.dll bin/native/ 2>/dev/null || true
+    echo "✓ Rust libraries built"
+fi
+
+echo ""
+echo "Libraries available in bin/native/"
+ls -la bin/native/ 2>/dev/null || echo "No libraries found"