Extract Generator System to Separate Gem/Engine

[frogr]

Problem

The Hub generator system is tightly coupled to the main application.

Tasks

• Create Rails engine for generator functionality
• Define clear interfaces between app and generator
• Extract transformers to strategy pattern
• Implement generator configuration DSL

Acceptance Criteria

• Create engines/hub_generator/ directory
• Generator can run independently
• Clear contract between app and generator
• All generator specs pass
• Add integration tests for generator engine

Files to modify

• Move all files from lib/hub/ to engine
• Update app/services/generator_execution_service.rb
• Create engine structure

Phase: 4 (UI/Advanced)
Priority: Medium