Add Object, Interface, and Input type components with tests

[FionaBronwen]

Summary

Add Object, Interface, and Input type components for rendering GraphQL type declarations.

• ObjectType - Renders GraphQL object types with fields, interface implementations, and operation fields
• InterfaceType - Renders GraphQL interface types (models marked with @Interface)
• InputType - Renders GraphQL input object types

This PR builds on #86 (mutation engine fixes) which ensures all type naming is handled during mutation, so components can simply use type.name directly.

Changes

New Components

ObjectType (src/components/types/object-type.tsx)

• Renders model properties as GraphQL fields
• Supports interface implementations via @compose decorator
• Supports operation fields via @operationFields decorator

InterfaceType (src/components/types/interface-type.tsx)

• Renders models marked with @Interface as GraphQL interface types
• Includes all model properties as interface fields

InputType (src/components/types/input-type.tsx)

• Renders input object types for operation parameters
• The mutation engine handles the "Input" suffix naming

Simplification

Removed the modelVariants lookup from InputType and GraphQLTypeExpression since the mutation engine now handles all input/output type naming. Components use type.name directly.

Test plan

• ObjectType tests (10 tests) - fields, descriptions, interfaces, operation fields, empty type
  error
• InterfaceType tests (5 tests) - fields, descriptions, empty type error
• InputType tests (7 tests) - fields, descriptions, arrays, empty type error
• All 187 tests pass