debug(ci): print SSH key fingerprint to verify key integrity

.gitea/workflows/build.yml

@@ -54,8 +54,9 @@ jobs:
           apk add --no-cache openssh-client
 
           # Installer la clé privée dans /tmp (filesystem accessible en écriture)
-          printf '%s' "${{ secrets.SSH_PRIVATE_KEY }}" > /tmp/id_ed25519
+          echo "${{ secrets.SSH_PRIVATE_KEY }}" > /tmp/id_ed25519
           chmod 600 /tmp/id_ed25519
+          ssh-keygen -l -f /tmp/id_ed25519
 
           SSH="ssh -i /tmp/id_ed25519 -o StrictHostKeyChecking=no -o ConnectTimeout=10 -o BatchMode=yes Stude12@192.168.1.39"