style: fix formatting and add newlines at end of files

backend/src/main/java/de/szut/casino/security/GoogleController.java

@@ -46,4 +46,4 @@ public class GoogleController {
         AuthResponseDto response = googleService.processGoogleCode(code);
         return ResponseEntity.ok(response);
     }
-}
+}

backend/src/main/java/de/szut/casino/security/GoogleService.java

@@ -161,4 +161,4 @@ public class GoogleService {
             throw new RuntimeException("Failed to process Google authentication", e);
         }
     }
-}
+}

backend/src/main/java/de/szut/casino/security/oauth2/GoogleOAuth2UserInfo.java

@@ -22,4 +22,4 @@ public class GoogleOAuth2UserInfo extends OAuth2UserInfo {
     public String getEmail() {
         return (String) attributes.get("email");
     }
-}
+}