fix(deps): remove redundant webauthn4j-core direct dependency

The webauthn4j-core implementation dependency was added by mistake.
Spring Security's spring-security-webauthn already provides it
transitively, and the codebase has no direct imports of
com.webauthn4j.* classes. Keeping it as an implementation dependency
unnecessarily forces it onto consuming applications.

Closes #280

Author: devondragon

build.gradle

@@ -53,7 +53,6 @@ dependencies {
 
     // WebAuthn support (Passkey authentication)
     compileOnly 'org.springframework.security:spring-security-webauthn'
-    implementation 'com.webauthn4j:webauthn4j-core:0.31.1.RELEASE'
 
     // Lombok dependencies
     compileOnly "org.projectlombok:lombok:$lombokVersion"