feat(flutter-cursor-templates): introduce MCP integration and conventions in project brief

- Added optional MCP integration settings in project-brief.yaml, allowing for environment-based server configurations.
- Introduced conventions for strict package imports to enhance code organization and maintainability.
- Updated brief schema to validate new MCP properties and ensure correct usage.
- Implemented MCP JSON builder to generate .cursor/mcp.json based on project brief settings.
- Enhanced resolver to include MCP configuration in generated files when enabled.

This update improves integration capabilities and enforces coding standards across the project.

flutter-cursor-templates/templates/root/lefthook.yaml.tmpl

@@ -1,4 +1,5 @@
 # {{PROJECT_NAME}} — generated by cursor_gen; adjust commands to your repo
+# Optional: run `bash tool/cursor_audit.sh` after changing features.modules or rule files.
 pre-commit:
   commands:
     flutter-analyze: