fix(token-registry): convert CIP-26 logo from hex to base64 before re…

[ghost]

Fixes: #748

Summary

When the token registry API returns logo data for CIP-26 tokens, the logo.value field contained raw hex-encoded bytes (e.g.89504e470d0a…) instead of the base64-encoded string that the CIP-26 specification and the LogoType.format = "base64" contract both require. This broke logo rendering in every consuming client (wallets,dApps) that treated the value as a base64 image URI.

Changes

Fix — TokenRegistryServiceImpl

• Added @Slf4j for structured warning logs.

• Extracted a new private helper encodeLogoValue() that converts a
  hex string to standard base64 using HexFormat and Base64 from
  java.util (no new dependencies).

• Updated convertToLogoData() to call the helper for CIP-26 logos.
  Edge cases handled:

  Input	Behaviour
  Valid hex	Converted to base64 ✅
  null value	Returns LogoData { format: BASE64, value: null } (unchanged)
  Empty string	Returns null logo (field omitted)
  Malformed hex (odd length)	Returns null logo + WARN log
  CIP-68 URL	Passed through unchanged ✅

Tests — TokenRegistryServiceImplTest

• Updated shouldConvertCip26LogoToBase64: now passes real hex input
  and asserts the correctly converted base64 output.
• Updated shouldHandleCaseInsensitiveCipStandards: uses valid hex and
  asserts base64 output.
• Updated shouldExtractCompleteMetadataWhenFullDataAvailable: helper
  now uses valid hex logo fixture.
• Added shouldReturnNullLogoForMalformedHex (odd-length hex → null).
• Added shouldReturnNullLogoForEmptyHexValue (empty string → null).
• Added shouldNotConvertCip68UrlLogo (CIP-68 URL regression guard).

Behavioral tests

• network_test_data.yaml: updated logo_value_prefix from"89504e47" (hex PNG magic bytes) to "iVBORw" (base64 PNG prefix) for all CIP-26 tokens on preprod and mainnet.
• test_token_registry.py: parity test now converts the upstream registry's raw hex value to base64 before comparing with Rosetta's response.
• network_options_operation_types.json: bumped middleware_version from 2.1.2 to 2.2.0.

[github-actions]

❌ Preprod Tests: FAILED

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🔗 Action Run #335

Tests run against preprod network with live blockchain data

[github-actions]

❌ Preprod Tests: FAILED

📊 View Detailed Test Report

🔗 Action Run #337

Tests run against preprod network with live blockchain data

[github-actions]

✅ Preprod Tests: PASSED

📊 View Detailed Test Report

🔗 Action Run #342

Tests run against preprod network with live blockchain data