fix: let install subprocess start pured daemon to avoid ETXTBSY

Pre-starting pured in the entrypoint caused ETXTBSY when the install
subprocess (triggered by createRootProcessForMissingComponents) tried
to overwrite the running daemon binary.

- Remove pured pre-start from entrypoint; daemon starts via
  `systemctl start pured` inside the install subprocess instead
- systemctl stop: use pkill -9 + sleep 1 for reliable termination
- systemctl start: wait up to 15s for :9485 instead of blind sleep 2

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

vpn-node/systemctl.sh

@@ -7,9 +7,14 @@ case "$*" in
         echo "inactive"; exit 1 ;;
     *"start pured"*)
         NODE_ENV=production /opt/purevpn-cli/pured-linux-x64 --start &
-        sleep 2; exit 0 ;;
+        for _i in $(seq 1 15); do
+            nc -z 127.0.0.1 9485 2>/dev/null && exit 0
+            sleep 1
+        done
+        exit 0 ;;
     *"stop pured"*|*"disable pured"*)
-        pkill -f "pured-linux-x64" 2>/dev/null || true; exit 0 ;;
+        pkill -9 -f "pured-linux-x64" 2>/dev/null || true
+        sleep 1; exit 0 ;;
     *)
         exit 0 ;;
 esac