Add TODO for NotificationCenter implementation and SVG images

TODO.md

@@ -0,0 +1,12 @@
+# NotificationCenter - Responsive Image srcSet Implementation
+
+## Progress Tracking
+
+- [x] Step 0: Analyze codebase and create plan (complete)
+- [ ] Step 1: Create notification SVG images for responsive breakpoints
+- [ ] Step 2: Create `NotificationCenter.css` with design token styles
+- [ ] Step 3: Create `NotificationCenter.tsx` with `<picture>` + `srcSet` pattern
+- [ ] Step 4: Create `NotificationCenter.test.tsx` with focused tests
+- [ ] Step 5: Update `src/App.tsx` to add `/notifications` route
+- [ ] Step 6: Run tests and verify build
+