Add admin instance management and system tools

- Implemented sync_dev_hosts.sh for managing local hosts entries for development.
- Created admin_instances.html for managing school instances, including creation and listing.
- Developed admin_system.html for core services management, including restart and backup operations.
- Added my_instance.html for users to view and manage their assigned instances.
- Introduced provision_instance.sh for provisioning new instances with Docker, including Nginx configuration and SSL certificate handling.

Website/launch_prod.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$SCRIPT_DIR"
+
+export SESSION_COOKIE_SECURE="1"
+export INSTANCE_TLS_MODE="production"
+export INSTANCE_PARENT_DOMAIN="${INSTANCE_PARENT_DOMAIN:-meine-domain}"
+export INSTANCE_WILDCARD_CERT_FILE="${INSTANCE_WILDCARD_CERT_FILE:-/etc/nginx/certs/wildcard.meine-domain.crt}"
+export INSTANCE_WILDCARD_KEY_FILE="${INSTANCE_WILDCARD_KEY_FILE:-/etc/nginx/certs/wildcard.meine-domain.key}"
+
+if [[ ! -f "$INSTANCE_WILDCARD_CERT_FILE" || ! -f "$INSTANCE_WILDCARD_KEY_FILE" ]]; then
+  echo "Error: Wildcard certificate missing for production mode"
+  echo "  CERT: $INSTANCE_WILDCARD_CERT_FILE"
+  echo "  KEY:  $INSTANCE_WILDCARD_KEY_FILE"
+  exit 1
+fi
+
+echo "Launching PRODUCTION stack"
+echo "  SESSION_COOKIE_SECURE=$SESSION_COOKIE_SECURE"
+echo "  INSTANCE_TLS_MODE=$INSTANCE_TLS_MODE"
+echo "  INSTANCE_PARENT_DOMAIN=$INSTANCE_PARENT_DOMAIN"
+echo "  INSTANCE_WILDCARD_CERT_FILE=$INSTANCE_WILDCARD_CERT_FILE"
+echo "  INSTANCE_WILDCARD_KEY_FILE=$INSTANCE_WILDCARD_KEY_FILE"
+
+docker compose build website
+docker compose up -d
+
+echo "Production stack is running on http://localhost:4999"
+echo "Provisioning expects wildcard certificate for all subdomains."