design-systems: add 74 brand DESIGN.md files (VoltAgent/awesome-design-md)

- 74 brands: airbnb, stripe, apple, figma, linear, vercel, etc.
- 147 files: DESIGN.md + README.md per brand (~2.1 MB)
- Each DESIGN.md contains structured brand analysis (colors, typography, components)
- Updated 00-overview.md with new design-systems directory

layout/overlapping-layers.md

@@ -0,0 +1,35 @@
+---
+name: layout/overlapping-layers
+title: Overlapping Elements
+description: Elements that overlap to create depth and visual interest.
+tags: [layout, overlapping, depth, premium]
+source: amppz.com, brad.co, stripe.com, linear.app
+---
+
+# Overlapping Elements
+
+## CSS
+
+```css
+.overlapping-grid {
+  display: grid;
+  grid-template-columns: repeat(12, 1fr);
+}
+.image-card {
+  grid-column: span 6;
+  z-index: 1;
+}
+.text-card {
+  grid-column: 7 / span 6;
+  margin-top: -60px;
+  z-index: 2;
+}
+```
+
+## Anti-patterns
+
+| ❌ Плохо | ✅ Хорошо |
+|----------|-----------|
+| Без `z-index` | `z-index: 1/2` |
+| `margin-top: -200px` | `margin-top: -30px` |
+| Без mobile fallback | `@media (max-width: 768px)` |