install_server: install all deps via requirements.txt, patch after

Reverts the split-install approach. volkswagencarnet stays in
server/requirements.txt; the patch is applied in a single step
after pip install completes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

install_server.sh

@@ -66,7 +66,6 @@ if patch -d "$SITE_PKG" -p1 -N --dry-run --silent < "$PATCH_FILE" 2>/dev/null; t
 else
     echo "    Patch already applied (skipping)"
 fi
-
 echo "    Python  : $PYTHON"
 echo ""