Add LICENSE and update .gitignore

- Add MIT License
- Ignore macos build directory and compiled binary
- Ignore DMG files

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

.gitignore

@@ -1,7 +1,9 @@
 # Build
-WhisperDictate
+macos/build/
+macos/WhisperDictate.app/Contents/MacOS/
 *.o
 *.dSYM/
+*.dmg
 
 # macOS
 .DS_Store