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/generator/templates/rules/features/_stub.mdc.tmpl

@@ -0,0 +1,21 @@
+---
+description: "Feature module {{FEATURE_MODULE}} — contracts, boundaries, and ownership (fill after design)"
+globs: ["lib/**/{{FEATURE_MODULE}}/**", "test/**/{{FEATURE_MODULE}}/**"]
+alwaysApply: false
+---
+
+# Feature — {{FEATURE_MODULE_TITLE}}
+
+## Context
+This stub was generated from `features.modules` in `project-brief.yaml`. Use it to capture **public contracts** (routes, DTOs, events) and **dependencies** for `{{FEATURE_MODULE}}` so agents do not invent cross-feature wiring.
+
+## Constraints
+- List external dependencies (other features, packages, backend endpoints) explicitly
+- Document invariants (auth required, idempotency, offline behavior) when known
+- Update or delete this file when the module is removed or renamed — run `bash tool/cursor_audit.sh` to catch drift
+
+## Patterns
+- Link to key entry points: primary screen(s), state holder(s), repository interface(s)
+
+## Anti-patterns
+- Empty file left forever — either fill it or delete the module entry from the brief