feat: add release build script for multi-platform binaries

- Add scripts/release.sh for automated release builds
- Creates tar.gz packages for Linux and macOS
- Generates SHA256 checksums
- Add 'make release' target
- Add releases/ to .gitignore

Usage:
  make release  # Build and package for all platforms

Output: releases/v0.2.5/*.tar.gz + SHA256SUMS.txt

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.gitignore

@@ -41,3 +41,4 @@ Network Trash Folder
 Temporary Items
 .apdisk
 
+releases/