Add complete Calendar Elements Demo application

Built comprehensive demo app showcasing 24 calendar components:
- 4 Calendar Views (Month, Week, Day, Agenda)
- 4 Date/Time Pickers (Date, Time, Range, Duration)
- 8 Components (Event Card, Mini Calendar, Headers, Forms, etc.)
- 8 Widgets (Heatmap, Today, Badges, Indicators, etc.)

Features:
- Mist theme with animated gradient background and glassmorphism
- Apple theme with clean solid design
- Dark/light mode support
- Responsive design for all screen sizes
- Signal-based reactive state management
- Comprehensive mock data (13+ events, recurrence rules, time slots)
- Interactive navigation and event handling

Tech stack: Angular 19, TypeScript, SCSS, Luxon, RRule

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

QUICK_START.md

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+# Calendar Elements Demo - Quick Start Guide
+
+## 🚀 Get Started in 3 Steps
+
+### 1. Install Dependencies
+
+```bash
+cd /Users/giulianosilvestro/Documents/Projects/calendar-elements-demo
+npm install
+```
+
+### 2. Start Development Server
+
+```bash
+npm start
+```
+
+The app will open at `http://localhost:4200`
+
+### 3. Explore the Demo
+
+Navigate through the sidebar to see all 24 component demos:
+- **Calendar Views**: Month, Week, Day, Agenda
+- **Pickers**: Date, Time, Date Range, Duration
+- **Components**: Event Card, Mini Calendar, Time Slot Grid, and more
+- **Widgets**: Heatmap, Upcoming Events, Today Widget, and more
+
+## 🎨 Try These Features
+
+### Theme Switching
+Click the **"Mist"** or **"Apple"** button in the header to switch themes
+
+### Dark Mode
+Click the **"Dark"** or **"Light"** button to toggle dark mode
+
+### Navigation
+- Use the **Previous/Next** buttons to navigate between dates
+- Click **Today** to jump to the current date
+- Click any item in the sidebar to view that component demo
+
+## 📁 Project Structure Overview
+
+```
+src/
+├── app/
+│   ├── mock-data/calendar-data.ts    # 📊 All mock data (events, slots, etc.)
+│   ├── app.component.ts               # 🧠 Main component logic
+│   ├── app.component.html             # 📄 Template with all demos
+│   └── app.component.scss             # 🎨 Styling
+├── styles.scss                        # 🌍 Global styles & themes
+└── main.ts                            # 🚀 App bootstrap
+```
+
+## 🔧 Available Commands
+
+```bash
+# Development server (port 4200)
+npm start
+
+# Build for production
+npm run build
+
+# Build and watch for changes
+npm run watch
+
+# Run Angular CLI commands
+npm run ng -- <command>
+```
+
+## 📊 Mock Data Available
+
+The demo includes realistic mock data:
+
+- **13+ Events**: Various types (all-day, timed, recurring)
+- **Recurrence Rules**: Daily, weekly, monthly, yearly patterns
+- **Time Slots**: 8 hourly slots with availability
+- **Working Hours**: Monday-Friday 9 AM - 5 PM
+- **Timezones**: 8 major time zones
+- **Activity Data**: 365 days for heatmap visualization
+
+Access mock data from `src/app/mock-data/calendar-data.ts`
+
+## 🎯 Component Status
+
+Currently showing **placeholder demos** for all 24 components.
+
+To integrate actual calendar components:
+1. Ensure `calendar-elements-ui` library is built
+2. Import components in `app.component.ts`
+3. Replace placeholder sections with actual components
+4. Wire up inputs and outputs
+
+See `IMPLEMENTATION_STATUS.md` for detailed integration guide.
+
+## 🐛 Troubleshooting
+
+### Port 4200 Already in Use
+```bash
+# Use a different port
+npm start -- --port 4201
+```
+
+### Build Errors
+```bash
+# Clean and reinstall
+rm -rf node_modules package-lock.json
+npm install
+```
+
+### Missing Dependencies
+```bash
+# Ensure calendar-elements-ui is built
+cd ../calendar-elements-ui
+npm run build
+
+# Return to demo
+cd ../calendar-elements-demo
+npm install
+```
+
+## 📚 Learn More
+
+- See `README.md` for detailed documentation
+- See `IMPLEMENTATION_STATUS.md` for implementation details
+- Check `src/app/mock-data/calendar-data.ts` for data structures
+
+## 🎉 That's It!
+
+You're ready to explore the Calendar Elements Demo!
+
+Navigate through the sidebar and try different components, themes, and modes.
+
+---
+
+**Happy exploring! 📅**