Fix update instructions: set GIT_TOKEN before curl call

The example was missing "export GIT_TOKEN=...", causing an empty
Authorization header when copy-pasted as-is.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -161,6 +161,7 @@ Script zieht per `git pull`, aktualisiert die Python-Abhängigkeiten und
 startet den systemd-Service neu. Auf dem **Proxmox-Host** ausführen:
 
 ```bash
+export GIT_TOKEN=<dein-token>
 CTID=113 bash <(curl -fsSL -H "Authorization: token ${GIT_TOKEN}" \
   https://gitea.teamthiele.de/ethiele/linkvault/raw/branch/main/scripts/proxmox/update-linkvault.sh)
 ```