- Added AttrMap and AttrKey classes for type-safe attribute storage.
- Implemented AppAssetsAttrs and SkillAttrs for managing application and skill attributes.
- Refactored Sandbox and initializers to utilize the new attribute management system, enhancing modularity and clarity in asset handling.
- Add AppAssetsInitializer to load published app assets into sandbox
- Refactor VMFactory.create() to VMBuilder with builder pattern
- Extract SandboxInitializer base class and DifyCliInitializer
- Simplify SandboxLayer constructor (remove options/environments params)
- Fix circular import in sandbox module by removing eager SandboxBashTool export
- Update SandboxProviderService to return VMBuilder instead of VirtualEnvironment
