refactor: rename ui-developer agent to ui-expert and bump version

Renamed the ui-developer agent to ui-expert for better clarity and
consistency with naming conventions. This change affects both the root
project and the create-agentic-app template.

Changes made:
- Renamed .claude/agents/ui-developer.md to ui-expert.md in both root and template
- Updated agent name and references within agent configuration
- Bumped create-agentic-app version from 1.1.14 to 1.1.15
- Updated corresponding package-lock.json with new version

The agent's functionality and responsibilities remain unchanged - this is
purely a naming improvement to better reflect its role as a UI expert
rather than just a developer.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

create-agentic-app/package.json

@@ -1,6 +1,6 @@
 {
   "name": "create-agentic-app",
-  "version": "1.1.14",
+  "version": "1.1.15",
   "description": "Scaffold a new agentic AI application with Next.js, Better Auth, and AI SDK",
   "type": "module",
   "bin": {