docs: rebrand Certifai -> Prüfwerk (user-facing name)

The product is renamed Certifai -> Prüfwerk. This changes only the user-facing
brand text in the documentation (docs/**, VitePress title/name). It does NOT
touch functional identifiers that happen to contain "certifai" (the Docker
network, Keycloak realm/client, Harbor image project, the compliance-* crate
names, or the repo name) — those are infra-coupled and need a separate,
coordinated migration.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EgxGHn22YEfQz5fLHSHkLv

docs/guide/sbom.md

@@ -6,7 +6,7 @@ The SBOM (Software Bill of Materials) feature provides a complete inventory of a
 
 A Software Bill of Materials is a list of every component (library, package, framework) that your software depends on, along with version numbers, licenses, and known vulnerabilities. SBOMs are increasingly required for compliance audits, customer security questionnaires, and supply chain transparency.
 
-Certifai generates SBOMs automatically during each scan using Syft for dependency extraction and OSV.dev + NVD for vulnerability matching.
+Prüfwerk generates SBOMs automatically during each scan using Syft for dependency extraction and OSV.dev + NVD for vulnerability matching.
 
 ## Packages Tab