Upgrade commons-codec:commons-codec to 1.14 or higher to fix security vulnerability

The security vulnerability tool Snyk [identifies a security issue](https://security.snyk.io/vuln/SNYK-JAVA-COMMONSCODEC-561518) with `java-genai` using `commons-codec:commons-codec@1.11` (which was released on Oct 17, 2017, so 8.5 years ago). From the listing:

> [commons-codec:commons-codec](https://commons.apache.org/proper/commons-codec) is a package that contains simple encoder and decoders for various formats such as Base64 and Hexadecimal.
>
> Affected versions of this package are vulnerable to Information Exposure. When there is no byte array value that can be encoded into a string the Base32 implementation does not reject it, and instead decodes it into an arbitrary value which can be re-encoded again using the same implementation. This allows for information exposure exploits such as tunneling additional information via seemingly valid base 32 strings.

Snyk recommends upgrading to version 1.14 or higher. The latest version of `commons-codec:commons-codec` as of this writing is [1.21.0](https://mvnrepository.com/artifact/commons-codec/commons-codec/1.21.0), released January 30, 2026.