Add FXMacroData integration client

[roberttidball]

Summary

• Add a Java 21 FXMacroData client under quantasma-integrations.
• Cover macro, FX, COT, commodity, curve, differential, session, news, press release, GraphQL, and custom endpoint requests.
• Add a Spock spec using an injectable transport for offline request validation.

Tests

• mvn -pl quantasma-integrations -am -Dtest=FxMacroDataClientSpec -Dsurefire.failIfNoSpecifiedTests=false test
• Note: the current Maven setup compiles the integration module but does not run Groovy specs in this module.