feat: create ai-elements-ui demo application

Demo app showcasing ai-elements-ui components:
- AI Canvas with resizable split-panel layout
- Conversation history sidebar
- Avatar with animated states (idle, thinking, speaking)
- Typing indicators (dots, pulse, wave variants)
- Confidence meters (bar, gauge, dots, ring variants)
- Code blocks with syntax highlighting
- Skeleton loaders for various content types

Uses base-ui design tokens and Apple theme for styling.

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

package.json

@@ -10,6 +10,7 @@
   },
   "private": true,
   "dependencies": {
+    "@angular/animations": "^19.2.0",
     "@angular/common": "^19.2.0",
     "@angular/compiler": "^19.2.0",
     "@angular/core": "^19.2.0",
@@ -17,6 +18,8 @@
     "@angular/platform-browser": "^19.2.0",
     "@angular/platform-browser-dynamic": "^19.2.0",
     "@angular/router": "^19.2.0",
+    "ai-elements-ui": "file:../ai-elements-ui/dist",
+    "base-ui": "file:../sda-frontend/libs/base-ui/dist",
     "rxjs": "~7.8.0",
     "tslib": "^2.3.0",
     "zone.js": "~0.15.0"