Remove diagnostic steps for registry login from Docker build workflow

- Eliminate previous checks for registry login credentials, including Basic-Auth and token request diagnostics.
- Streamline the workflow by focusing on essential steps for Gitea Container Registry login.

.gitea/workflows/docker-build.yml

@@ -28,36 +28,6 @@ jobs:
       - name: Docker Buildx einrichten
         uses: docker/setup-buildx-action@v3
 
-      - name: Registry-Anmeldung prüfen (Diagnose)
-        env:
-          REG_USER: ${{ secrets.REGISTRY_USER || github.repository_owner }}
-          REG_TOKEN: ${{ secrets.REGISTRY_TOKEN }}
-        run: |
-          IMAGE_LOWER=$(echo "${IMAGE_NAME}" | tr '[:upper:]' '[:lower:]')
-          echo "Registry:      ${REGISTRY}"
-          echo "Username:       '${REG_USER}'  (Laenge: ${#REG_USER})"
-          echo "Token gesetzt:  $([ -n "${REG_TOKEN}" ] && echo ja || echo NEIN)  (Laenge: ${#REG_TOKEN})"
-          echo "Image (lower):  ${IMAGE_LOWER}"
-
-          echo "--- API-Test: /api/v1/user (Basic-Auth gueltig?) ---"
-          curl -s -o /dev/null -w "HTTP %{http_code}\n" -u "${REG_USER}:${REG_TOKEN}" "https://${REGISTRY}/api/v1/user"
-
-          echo "--- /v2/ Challenge (WWW-Authenticate) ---"
-          HDR=$(curl -s -D - -o /dev/null "https://${REGISTRY}/v2/")
-          AUTH=$(printf '%s' "$HDR" | tr -d '\r' | grep -i '^www-authenticate:' || true)
-          echo "${AUTH:-(keine WWW-Authenticate Zeile)}"
-          REALM=$(printf '%s' "$AUTH" | sed -n 's/.*realm="\([^"]*\)".*/\1/p')
-          SERVICE=$(printf '%s' "$AUTH" | sed -n 's/.*service="\([^"]*\)".*/\1/p')
-          echo "realm='${REALM}'  service='${SERVICE}'"
-
-          if [ -n "${REALM}" ]; then
-            echo "--- Token-Request am echten realm ---"
-            CODE=$(curl -s -o /tmp/tok.json -w "%{http_code}" -u "${REG_USER}:${REG_TOKEN}" \
-              "${REALM}?service=${SERVICE}&scope=repository:${IMAGE_LOWER}:pull,push")
-            echo "HTTP ${CODE}"
-            echo "Antwort (gekuerzt): $(head -c 300 /tmp/tok.json)"
-          fi
-
       - name: An Gitea Container Registry anmelden
         uses: docker/login-action@v3
         with: