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/getting-started.md

@@ -1,10 +1,10 @@
 # Getting Started
 
-Certifai is an AI-powered security compliance platform that scans your Git repositories for vulnerabilities, builds software bills of materials, performs dynamic application testing, and provides code intelligence through an interactive knowledge graph and AI chat.
+Prüfwerk is an AI-powered security compliance platform that scans your Git repositories for vulnerabilities, builds software bills of materials, performs dynamic application testing, and provides code intelligence through an interactive knowledge graph and AI chat.
 
 ## What You Get
 
-When you connect a repository, Certifai runs a comprehensive scan pipeline that covers:
+When you connect a repository, Prüfwerk runs a comprehensive scan pipeline that covers:
 
 - **Static Analysis (SAST)** -- finds code-level vulnerabilities like injection flaws, insecure crypto, and misconfigurations
 - **Software Bill of Materials (SBOM)** -- inventories every dependency, its version, and its license