feat(perf): swap 4G->8G via second swapfile, applied live [#755]

Applied on my.knownelement.com 2026-09-03 (founder-approved):
/apps.swap2 4G, fstab-persisted, no restarts. Verification + closure
note: https://projects.knownelement.com/issues/755#note-13

perf/swap/grow-swap2.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+# grow-swap2.sh — add a second 4G swapfile on the Cloudron host [#755]
+# Founder-approved 2026-09-03. Second-file approach: no swapoff, no restart,
+# zero risk to the running fleet. Idempotent — safe to re-run.
+#
+# Applied live on my.knownelement.com 2026-09-03 (result: /apps.swap +
+# /apps.swap2 = 8G total, fstab persisted). Re-runnable on any host that
+# needs the same headroom; set NEW/SIZE_MB to taste.
+set -euo pipefail
+
+NEW=/apps.swap2
+SIZE_MB=4096
+
+if swapon --show=NAME --noheadings | grep -qx "$NEW"; then
+  echo "$NEW already active"
+else
+  if [ -e "$NEW" ]; then
+    echo "ERROR: $NEW exists but is not active — inspect manually" >&2
+    exit 1
+  fi
+  fallocate -l "${SIZE_MB}M" "$NEW" 2>/dev/null \
+    || dd if=/dev/zero of="$NEW" bs=1M count="$SIZE_MB" status=none
+  chmod 600 "$NEW"
+  mkswap "$NEW"
+  swapon "$NEW"
+  echo "activated $NEW"
+fi
+
+if grep -q "^$NEW " /etc/fstab; then
+  echo "fstab entry already present"
+else
+  printf '%s none swap sw 0 0\n' "$NEW" >> /etc/fstab
+  echo "fstab entry added"
+fi
+
+echo "--- swapon ---"
+swapon --show
+echo "--- free ---"
+free -h