fix(deploy): Backend-Healthcheck und Staging-Wrapper absichern

Expliziter Compose-Healthcheck für das Backend, curl-Fallback und längeres
MAX_WAIT im Deploy-Skript; update-staging.sh lehnt -dest ab.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/update-staging.sh

@@ -1,5 +1,16 @@
 #!/bin/bash
 # Backward-compatible wrapper — prefer: ./scripts/update-prod.sh -dest stage
 set -euo pipefail
+
+for arg in "$@"; do
+  case "$arg" in
+    -dest|-dest=*)
+      echo "Error: update-staging.sh always deploys to staging." >&2
+      echo "       Use ./scripts/update-prod.sh -dest prod for production." >&2
+      exit 1
+      ;;
+  esac
+done
+
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 exec "$SCRIPT_DIR/update-prod.sh" -dest stage "$@"