chore: Flutter mobile app, CI, and dev tooling

- mobile/: Flutter/Dart merchant mobile app skeleton
- .github/: GitHub Actions CI workflows
- .dockerignore: exclude host node_modules from build context
- .cursorrules: Cursor IDE project rules
- .claude/: Claude Code project settings and launch config

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

mobile/meezi_app/analysis_options.yaml

@@ -0,0 +1,5 @@
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  rules:
+    prefer_const_constructors: true