Add VPS IMAP sorting automation

Prompts used since the previous commit:
- Hieronder staat je oorspronkelijke plan. Volgens mij moet stap 'Add VPS automation' nog worden uitgevoerd, inclusief de testen.

Special observations:
- Added a testable IMAP sorting daemon, shared IMAP operation helpers, systemd service template, and SSH deployment script.
- Local tests passed; no live VPS deployment or mailbox-affecting daemon test was run.
- verplaats_log.json remains modified from the user's run and was intentionally not staged.

deploy_vps.sh

@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+VPS_HOST="${VPS_HOST:-vps.austalius.nl}"
+VPS_USER="${VPS_USER:?Set VPS_USER to the non-root sudo SSH user}"
+APP_USER="${APP_USER:-mailcat}"
+APP_DIR="${APP_DIR:-/opt/mailcat}"
+SERVICE_NAME="${SERVICE_NAME:-mailcat-sort-backup}"
+ACCOUNT="${ACCOUNT:-backup}"
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ARCHIVE="$(mktemp -t mailcat-deploy.XXXXXX.tar.gz)"
+
+cleanup() {
+  rm -f "$ARCHIVE"
+}
+trap cleanup EXIT
+
+tar \
+  --exclude ".git" \
+  --exclude "__pycache__" \
+  --exclude "mailbox" \
+  --exclude "config.json" \
+  --exclude "*.log" \
+  --exclude "backup_log.json" \
+  --exclude "verplaats_log*.json" \
+  --exclude "sort_mail_daemon_state.json" \
+  --exclude "mailing_lists_cache*.json" \
+  --exclude "*.pyc" \
+  -C "$ROOT_DIR" \
+  -czf "$ARCHIVE" .
+
+scp "$ARCHIVE" "$VPS_USER@$VPS_HOST:/tmp/mailcat-deploy.tar.gz"
+
+ssh "$VPS_USER@$VPS_HOST" \
+  "APP_USER='$APP_USER' APP_DIR='$APP_DIR' SERVICE_NAME='$SERVICE_NAME' ACCOUNT='$ACCOUNT' bash -s" <<'REMOTE'
+set -euo pipefail
+
+if ! id "$APP_USER" >/dev/null 2>&1; then
+  sudo useradd --system --home "$APP_DIR" --shell /usr/sbin/nologin "$APP_USER"
+fi
+
+sudo mkdir -p "$APP_DIR" /var/lib/mailcat /var/log/mailcat
+sudo tar -xzf /tmp/mailcat-deploy.tar.gz -C "$APP_DIR"
+sudo chown -R "$APP_USER:$APP_USER" "$APP_DIR" /var/lib/mailcat /var/log/mailcat
+sudo chmod 750 "$APP_DIR"
+
+if [ ! -f "$APP_DIR/config.json" ]; then
+  echo "Missing $APP_DIR/config.json on VPS. Create it with mode 600 before starting the service." >&2
+fi
+sudo chmod 600 "$APP_DIR/config.json" 2>/dev/null || true
+sudo chown "$APP_USER:$APP_USER" "$APP_DIR/config.json" 2>/dev/null || true
+
+sudo install -m 0644 "$APP_DIR/systemd/mailcat-sort.service" "/etc/systemd/system/$SERVICE_NAME.service"
+sudo sed -i \
+  -e "s#__APP_USER__#$APP_USER#g" \
+  -e "s#__APP_DIR__#$APP_DIR#g" \
+  -e "s#__ACCOUNT__#$ACCOUNT#g" \
+  "/etc/systemd/system/$SERVICE_NAME.service"
+
+sudo systemctl daemon-reload
+sudo systemctl enable "$SERVICE_NAME.service"
+
+echo "Deployment complete."
+echo "Create/check $APP_DIR/config.json, then run:"
+echo "  sudo systemctl start $SERVICE_NAME.service"
+echo "  sudo journalctl -u $SERVICE_NAME.service -f"
+REMOTE