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/.cursorignore.tmpl

@@ -0,0 +1,27 @@
+# Build artefacts
+build/
+.dart_tool/
+.flutter-plugins
+.flutter-plugins-dependencies
+*.g.dart
+*.freezed.dart
+*.gr.dart
+*.config.dart
+
+# Secrets
+.env
+.env.*
+firebase_options.dart
+google-services.json
+GoogleService-Info.plist
+
+# Large binary assets
+assets/fonts/
+assets/videos/
+*.aab
+*.apk
+*.ipa
+
+# IDE
+.idea/
+*.iml