[MCP] Add Export/Import functionality for MCP Configurations

[onbuyuka]

Summary

Adds the ability to export and import MCP server configurations as JSON files, enabling users to easily share configurations across different Business Central environments.

Changes

New Features

• Export Configuration: Export an MCP configuration (including all tools and permissions) to a JSON file
• Import Configuration: Import an MCP configuration from a JSON file, with automatic name conflict detection

UI Changes

• Added Export and Import actions to the "Advanced" action group on the MCP Config List page
• Both actions are promoted for easy access
• Changed the "Connection String" action icon from Export to Link to avoid visual confusion with the new Export action
• Enhanced the Copy Config dialog to display an instruction message when a name conflict is detected during import

Implementation Details

• Export creates a JSON file named MCPConfig_<name>_<date>.json containing:
  • Configuration settings (name, description, enableDynamicToolMode, discoverReadOnlyObjects, allowProdChanges)
  • All associated tools with their permissions
• Import always creates configurations as inactive (validation happens on activation)
• When importing a config with a name that already exists, displays a dialog prompting for a new name
• Added public API methods ExportConfiguration and ImportConfiguration to the MCP Config codeunit for extensibility

Files Modified

• MCPConfig.Codeunit.al - Added public API for export/import
• MCPConfigImplementation.Codeunit.al - Added export/import implementation logic
• MCPConfigList.Page.al - Added Export/Import actions
• MCPConfigCard.Page.al - Changed Connection String icon
• MCPCopyConfig.Page.al - Added instruction message field and setter methods
• MCPConfigTest.Codeunit.al - Added unit tests for export/import

Tests

• TestExportConfiguration - Verifies JSON export contains correct configuration data and tools
• TestImportConfiguration - Verifies import creates config with correct settings and tools

Fixes AB#619975