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/findings.md

@@ -116,7 +116,7 @@ When you mark a finding as a false positive, you are providing training signal t
 
 ## Human in the Loop
 
-Certifai uses AI to triage findings, but humans make the final decisions. Here is how the process works:
+Prüfwerk uses AI to triage findings, but humans make the final decisions. Here is how the process works:
 
 1. **AI triages** -- the LLM reviews each finding, assigns a severity, generates a confidence score, and writes a rationale explaining its assessment
 2. **You review** -- you read the AI's analysis alongside the code evidence and decide whether to act on it