Clean version management with generated version.js

- Replace package.json modification with generated src/version.js
- App imports VERSION from ./version instead of package.json
- version.js is auto-generated during prebuild and git-ignored
- Provides VERSION, IS_RELEASE, and BUILD_TIME constants
- No more dirty git status from version changes

Development builds show 1.0.4-dev, tagged releases show 1.0.4

demo.sh

@@ -41,6 +41,7 @@ npm test -- --watchAll=false
 
 echo ""
 echo "🔨 Building React application..."
+echo "  (Version will be automatically tagged as -dev since not building from git tag)"
 npm run build
 
 echo ""