Resolve OpenRewrite snapshots from the Code Genome Project in the Pages workflow

[timtebeek]

The Deploy plugin docs to Pages workflow fails to build the site:

Non-resolvable import POM: The following artifacts could not be resolved:
org.openrewrite:rewrite-bom:pom:8.92.0-SNAPSHOT (absent): Could not find artifact
org.openrewrite:rewrite-bom:pom:8.92.0-SNAPSHOT in ossrh-snapshots

Upstream OpenRewrite snapshots now live in the Code Genome Project repository rather than ossrh-snapshots. The codegenome profile in pom.xml adds that repository, but it activates on env.CODEGENOME_USERNAME, and pages.yml was the one workflow that never got those credentials wired up (ci.yml, publish.yml and bump-snapshots.yml all have them).

Mirrors the setup in ci.yml: server-id: codegenome on setup-java, plus the CODEGENOME_USERNAME/CODEGENOME_TOKEN env on the site step.