Use bare tokens: PAT_FOR_GITHUB replaces CREDENTIALS_FOR_GITHUB

The sync workflow reads secrets.PAT_FOR_GITHUB as clear text and
parse_github_token and parse_gitea_token only check that the value is not
empty. No secret is JSON any more; the wiki publisher follows. Update the
tests, the guides, the README, PP-001 UC candidate 2 and the wiki pages with
their Danish and Bahasa Malaysia translations.

Task: MIL-002#5

README.md

@@ -23,8 +23,8 @@ It currently contains the Gitea workflow [`sync-github-metadata.yml`](.gitea/sco
 - A Gitea instance with Actions enabled and a runner providing `ubuntu-latest` with `python3`
 - A configured GitHub push mirror on the Gitea repository (at most one; repositories without a mirror are skipped successfully)
 - Repository secrets:
-  - `TOKEN_FOR_GITEA`: Gitea API token (plain string, or JSON with `GITEA_TOKEN`)
-  - `CREDENTIALS_FOR_GITHUB`: JSON object containing `GITHUB_PAT`, a GitHub personal access token allowed to edit the mirror repository
+  - `TOKEN_FOR_GITEA`: Gitea API token (the token only, no JSON)
+  - `PAT_FOR_GITHUB`: a GitHub personal access token allowed to edit the mirror repository (the token only, no JSON)
   - `TOKEN_FOR_GITEA_WIKI` (optional, only in this repository, for the **Publish wiki** workflow): Gitea token that can write the repository wiki; when it is absent, `TOKEN_FOR_GITEA` is used and needs write access
 
 ## 🛠️ Setup
@@ -96,7 +96,7 @@ activate Workflow
 Workflow -> Workflow: Read and validate secrets
 note right
 TOKEN_FOR_GITEA
-CREDENTIALS_FOR_GITHUB
+PAT_FOR_GITHUB
 end note
 
 alt secret validation failed