refactor: add @EqualsAndHashCode by ID to assets-ext JPA entities
Aligns MetadataReferenceNftEntity, TokenLogoEntity and TokenMetadataEntity with the JPA entity convention used across the codebase: identity is defined by @Id fields only, using Lombok's @EqualsAndHashCode(onlyExplicitlyIncluded = true) plus @EqualsAndHashCode.Include on each @Id. This avoids proxy/lazy-loading pitfalls and matches the upstream yaci-store style. Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>