Description

Add comprehensive property-based tests using proptest for domain logic.

Tasks

• Property tests for value objects (ContentHash, StorageClass, etc.)
• Property tests for entity state transitions
• Property tests for validation logic
• Property tests for encoding/decoding operations
• Add regression test storage for found issues
• Document property testing patterns

Acceptance Criteria

• Proptest covers all domain entities and value objects
• Regression tests for discovered edge cases
• Properties documented in code

Metadata

• Priority: Medium
• Story Points: 5
• Component: Tests
• Sprint: Sprint 1
• Epic: Testing & Quality Assurance