Initial commit: Developer Tools MVP with visual editor

- Complete React app with 7 developer tools
- JSON Tool with visual structured editor
- Serialize Tool with visual structured editor
- URL, Base64, CSV/JSON, Beautifier, Diff tools
- Responsive navigation with dropdown menu
- Dark/light mode toggle
- Mobile-responsive design with sticky header
- All tools working with copy/paste functionality

node_modules/clean-css/lib/optimizer/level-1/property-optimizers.js

@@ -0,0 +1,10 @@
+module.exports = {
+  background: require('./property-optimizers/background').level1.property,
+  boxShadow: require('./property-optimizers/box-shadow').level1.property,
+  borderRadius: require('./property-optimizers/border-radius').level1.property,
+  filter: require('./property-optimizers/filter').level1.property,
+  fontWeight: require('./property-optimizers/font-weight').level1.property,
+  margin: require('./property-optimizers/margin').level1.property,
+  outline: require('./property-optimizers/outline').level1.property,
+  padding: require('./property-optimizers/padding').level1.property
+};