Implement `getNftMetadata`, `findNftTypesByOwner`, and `findAllNftTypes` for Spring and MicroProfile

## Summary

The NFT type APIs exposed by `MirrorNodeClient` / `NftRepository` are still not implemented in both enterprise stacks.

Right now:
- `AbstractMirrorNodeClient#getNftMetadata(TokenId)` throws `UnsupportedOperationException`
- Spring `MirrorNodeClientImpl#findNftTypesByOwner` and `findAllNftTypes` throw `UnsupportedOperationException`
- MicroProfile `MirrorNodeClientImpl#findNftTypesByOwner` and `findAllNftTypes` throw `RuntimeException("Not implemented")`

These should be implemented against the Hedera Mirror Node REST API for both `hiero-enterprise-spring` and `hiero-enterprise-microprofile`, with consistent behavior and test coverage.

## Scope

Implement support for:
- `getNftMetadata(TokenId)`: return token-level NFT metadata for an NFT class
- `findNftTypesByOwner(AccountId)`: return NFT token definitions for a given owner
- `findAllNftTypes()`: return all NFT token definitions

## Acceptance Criteria

- `getNftMetadata`, `findNftTypesByOwner`, and `findAllNftTypes` work in both Spring and MicroProfile
- `NftRepository` no longer hits stubs for these flows
- Pagination works for list endpoints
- Tests cover converter behavior and at least one paginated path
- No remaining `"Not implemented"` / `"Not yet implemented"` throws for these APIs