[Phase 6] Add Item, Site, and User context properties

[marioarce]

Task

Expand the context to include additional Sitecore context properties.

Deliverables

• Add Item property to ISitecoreThreadSafeContext
• Add Site property to ISitecoreThreadSafeContext
• Add User property to ISitecoreThreadSafeContext
• Update reflection provider to access these properties
• Update documentation
• Add unit tests for new properties
• Version bump to 1.1.0

Acceptance Criteria

• All three properties accessible via ThreadSafeContext
• Reflection-based access works for all properties
• Documentation updated
• Unit tests pass
• Version updated to 1.1.0