feat(ZEE-29): implement design system, dark mode, and JSON content management

- Add comprehensive design system with CSS variables, animations, and utility classes
- Implement dark mode with ThemeProvider (system preference + manual toggle)
- Create JSON-based content management system in src/content/
- Update all pages to use structured JSON content
- Add ThemeProvider component with theme toggle button
- Update Header with glass effect and animated mobile menu
- Update Footer with dark mode support
- Update documentation (README.md, CLAUDE.md, knowledge.md, proto/README.md)
- Sync with Linear (ZEE-29 completed)

README.md

@@ -44,7 +44,9 @@ This project uses **separated sync systems** for optimal management:
 
 ## 🛠️ Tech Stack
 
-- **Frontend**: Next.js 14, TypeScript, Tailwind CSS
+- **Frontend**: Next.js 14, TypeScript, Tailwind CSS 4
+- **Design System**: CSS Variables, Dark Mode, Custom Animations
+- **Content Management**: JSON-based structured content
 - **Backend**: Next.js API Routes, MongoDB
 - **Testing**: Jest, React Testing Library, Docker
 - **Deployment**: Dokploy, Docker
@@ -59,6 +61,9 @@ This project uses **separated sync systems** for optimal management:
 
 ### ✅ Completed Features
 - [x] Responsive website with modern design
+- [x] **Design System** with CSS variables, animations, and micro-interactions
+- [x] **Dark Mode** with system preference detection and manual toggle
+- [x] **JSON Content Management** - Structured, easily modifiable content system
 - [x] Contact form with validation & spam protection
 - [x] Rate limiting and security features
 - [x] Docker development environment
@@ -90,3 +95,37 @@ This project uses **separated sync systems** for optimal management:
 - [Traceability Matrix](./TRACEABILITY-MATRIX.md)
 - [Docker Setup](./DOCKER.md)
 - [Development Guide](./proto/README.md)
+
+## 🎨 Design System
+
+The project uses a comprehensive design system with:
+
+- **CSS Variables**: Brand colors, spacing, shadows, transitions
+- **Dark Mode**: Automatic system preference + manual toggle via ThemeProvider
+- **Animations**: fadeIn, float, pulse, hover effects (lift, scale, glow)
+- **Components**: Buttons, cards, icons with consistent styling
+
+## 📝 Content Management
+
+All website text content is managed through JSON files:
+
+```
+proto/src/content/
+├── types.ts          # TypeScript definitions
+├── index.ts          # Content loader utility
+├── common.json       # Shared texts (buttons, labels)
+└── pages/
+    ├── home.json     # Homepage content
+    ├── about.json    # About page content
+    ├── services.json # Services page content
+    └── contact.json  # Contact page content
+```
+
+**Usage:**
+```typescript
+import { content, getPageContent } from '@/content'
+
+// Access content
+const aboutContent = content.pages.about
+const servicesContent = getPageContent('services')
+```