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/commands/build.md.tmpl

@@ -0,0 +1 @@
+End-to-end feature implementation (research, TDD, integration tests, verification). Follow the workflow and constraints in `@file:.cursor/skills/build/SKILL.md`. Use `project-brief.yaml` as the source of truth for stack and platforms.

flutter-cursor-templates/generator/templates/commands/debug-issue.md.tmpl

@@ -0,0 +1 @@
+Structured bug triage and evidence-first debugging. Follow `@file:.cursor/skills/debug-issue/SKILL.md`. Gather reproduction steps, logs, and failing commands before proposing fixes.

flutter-cursor-templates/generator/templates/commands/explain-code.md.tmpl

@@ -0,0 +1 @@
+Explain-only walkthrough of code paths and stack behavior (no edits). Follow `@file:.cursor/skills/explain-code/SKILL.md`. Do not modify source files unless the user explicitly asks.

flutter-cursor-templates/generator/templates/commands/verify-change.md.tmpl

@@ -0,0 +1 @@
+Pre-PR verification checklist (analyze, tests, hooks) without full /build lifecycle. Follow `@file:.cursor/skills/verify-change/SKILL.md` for the change in scope.