feat(mpp-idea): enhance IdeaMcpConfigDialog UI to match ToolConfigDialog

1. McpServersTab improvements:
   - Add header row with title and real-time JSON validation status
   - Show validation status indicator (Loading/Invalid JSON/Valid JSON)
   - Add styled error container with icon for error details
   - Add border around JSON editor with error state styling
   - Add footer with example hint and Save & Reload button with icon
   - Use CircularProgressIndicator for loading states

2. Fix Icon component usage:
   - Change 'key =' to 'imageVector =' for all Icon components
   - Replace IdeaComposeIcons.Schedule with IdeaComposeIcons.History

3. UI consistency:
   - Match the design patterns from ToolConfigDialog.kt
   - Use consistent spacing, colors, and typography

Author: phodal