Support private repo access via Gitea token in Proxmox script

The repo is private, so unauthenticated curl/git clone returns 404.
Add GIT_TOKEN support for both the raw-file download and the git
clone inside the container, and document it in the README.

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

scripts/proxmox/install-linkvault.sh

@@ -32,6 +32,7 @@ TEMPLATE_STORAGE="${TEMPLATE_STORAGE:-local}"
 CT_PASSWORD="${CT_PASSWORD:-}"         # leer = zufällig generiert
 REPO_URL="${REPO_URL:-https://gitea.teamthiele.de/ethiele/linkvault.git}"
 APP_PORT="${APP_PORT:-8000}"
+GIT_TOKEN="${GIT_TOKEN:-}"             # Gitea Access Token, falls Repo privat ist
 
 # ---------------------------------------------------------------------------
 # Vorbedingungen
@@ -108,7 +109,11 @@ apt-get update -qq
 apt-get install -y -qq git python3 python3-venv python3-pip build-essential curl >/dev/null
 
 if [ ! -d /opt/linkvault ]; then
-  git clone --quiet '${REPO_URL}' /opt/linkvault
+  if [ -n '${GIT_TOKEN}' ]; then
+    git -c http.extraHeader=\"Authorization: token ${GIT_TOKEN}\" clone --quiet '${REPO_URL}' /opt/linkvault
+  else
+    git clone --quiet '${REPO_URL}' /opt/linkvault
+  fi
 fi
 cd /opt/linkvault