- Add null check to WorkspaceInvitation::isExpired() to prevent null errors
- Remove foreign key columns from protected $guarded to prevent silent mass-assignment drops in Workspace, Link, and Domain models
- Add explicit return types (HasMany, BelongsTo) to User relationship methods
- Add return type to Click::link() relationship method
- Add protected $casts for LinkVariant (weight, clicks_count, conversions_count)
Fixes code quality and type safety issues in domain models.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>