Design environment type configuration schema

**Summary**: Define the YAML schema structure for environment types, including predefined types, custom type definitions, and type-specific metadata.

**Acceptance Criteria**:
- [ ] YAML schema for environment type definitions with name, properties, and constraints
- [ ] Support for predefined types (dev, test, staging, prod) with default behaviors
- [ ] Custom environment type definition capability for organizations
- [ ] JSON schema validation for environment type configurations
- [ ] Documentation and examples for environment type schema