Fix script shebangs for better portability

Use #!/usr/bin/env bash instead of #!/bin/bash for better
compatibility across different systems.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/build.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Build script for Lumacs
 
 set -e  # Exit on error

scripts/clean.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Clean script for Lumacs - removes build artifacts and temporary files
 
 echo "Cleaning Lumacs build artifacts..."

scripts/test.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Test script for Lumacs
 
 set -e