Add build system for native applications

- PyInstaller spec file for cross-platform builds
- Build scripts for Linux/macOS (build.sh) and Windows (build.bat)
- requirements.txt with all dependencies
- Updated README with build and installation instructions
- Support for creating standalone executables for all platforms

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

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

word_search.spec

@@ -0,0 +1,51 @@
+# -*- mode: python ; coding: utf-8 -*-
+
+block_cipher = None
+
+a = Analysis(
+    ['word_search_generator.py'],
+    pathex=[],
+    binaries=[],
+    datas=[],
+    hiddenimports=[],
+    hookspath=[],
+    hooksconfig={},
+    runtime_hooks=[],
+    excludes=[],
+    win_no_prefer_redirects=False,
+    win_private_assemblies=False,
+    cipher=block_cipher,
+    noarchive=False,
+)
+
+pyz = PYZ(a.pure, a.zipped_data, cipher=block_cipher)
+
+exe = EXE(
+    pyz,
+    a.scripts,
+    a.binaries,
+    a.zipfiles,
+    a.datas,
+    [],
+    name='WordSearch',
+    debug=False,
+    bootloader_ignore_signals=False,
+    strip=False,
+    upx=True,
+    upx_exclude=[],
+    runtime_tmpdir=None,
+    console=False,  # No console window
+    disable_windowed_traceback=False,
+    argv_emulation=False,
+    target_arch=None,
+    codesign_identity=None,
+    entitlements_file=None,
+)
+
+# macOS app bundle
+app = BUNDLE(
+    exe,
+    name='WordSearch.app',
+    icon=None,
+    bundle_identifier='com.firebugit.wordsearch',
+)