README: badges, consistent structure, remove zero-dep messaging

Author: lgutschow

README.md

@@ -1,6 +1,11 @@
 # cyphera
 
-Data protection SDK for Java — format-preserving encryption (FF1/FF3), AES-GCM, data masking, and hashing. Zero runtime dependencies.
+[![CI](https://github.com/cyphera-labs/cyphera-java/actions/workflows/ci.yml/badge.svg)](https://github.com/cyphera-labs/cyphera-java/actions/workflows/ci.yml)
+[![Maven Central](https://img.shields.io/maven-central/v/io.cyphera/cyphera)](https://central.sonatype.com/artifact/io.cyphera/cyphera)
+[![Java](https://img.shields.io/badge/java-8%2B-orange)](https://www.oracle.com/java/)
+[![License](https://img.shields.io/badge/license-Apache%202.0-blue)](LICENSE)
+
+Data protection SDK for Java — format-preserving encryption (FF1/FF3), AES-GCM, data masking, and hashing.
 
 ## Install