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>

.gitignore

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+# See http://help.github.com/ignore-files/ for more about ignoring files.
+
+# Compiled output
+/dist
+/tmp
+/out-tsc
+/bazel-out
+
+# Node
+/node_modules
+npm-debug.log
+yarn-error.log
+
+# IDEs and editors
+.idea/
+.project
+.classpath
+.c9/
+*.launch
+.settings/
+*.sublime-workspace
+
+# Visual Studio Code
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+.history/*
+
+# Miscellaneous
+/.angular/cache
+.sass-cache/
+/connect.lock
+/coverage
+/libpeerconnection.log
+testem.log
+/typings
+
+# System files
+.DS_Store
+Thumbs.db