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/.vitepress/config.mts

@@ -2,7 +2,7 @@ import { defineConfig } from 'vitepress'
 import { withMermaid } from 'vitepress-plugin-mermaid'
 
 export default withMermaid(defineConfig({
-  title: 'Certifai',
+  title: 'Prüfwerk',
   description: 'AI-powered security compliance scanning platform',
   ignoreDeadLinks: [
     /localhost/,
@@ -54,7 +54,7 @@ export default withMermaid(defineConfig({
       { icon: 'github', link: 'https://gitea.meghsakha.com/sharang/compliance-scanner-agent' },
     ],
     footer: {
-      message: 'Certifai Documentation',
+      message: 'Prüfwerk Documentation',
     },
   },
   mermaid: {},