[Backend] Refactor project structure

[markgravity]

Why

• Missing required packages
• The old structure still bad and need more improvements

Acceptance Criteria

• Upddate with new project structure
• Include required packages:
  • get_it: dependency injection
  • flutter_platform_widgets: native widget base on current platform
  • dio: make http request
  • json_annotation
  • enumerated_class: enum support class
  • object_mapper: support convert json to object
  • streams_provider: state manager
  • shared_preferences: local storage
  • modal_progress_hud: block ui
  • adaptive_dialog: native dialog base on current platform
  • build_runner:
  • flutter_gen_runner: assets generator
  • lint
  • json_serializable