User can generate dedicated theme scaffolding

[lasomethingsomething]

User Story

As a theme developer, I want dedicated theme scaffolding so that I can start with a structure optimized for storefront development instead of adapting a generic plugin scaffold.

Acceptance criteria

• shopware extension create --type=theme generates a dedicated theme structure (not a generic plugin).
• The scaffold includes:
• Storefront Resources/views
• Storefront Resources/app/storefront
• Proper theme.json
• Preconfigured inheritance from storefront
• No follow-up questions required if --type=theme is provided.
• Generated theme installs and compiles without manual structural adjustments.