Add update.sh, persist Go on PATH via profile.d

update.sh pulls the latest main, rebuilds, reinstalls, and restarts
the service in one step. install.sh/bootstrap.sh now also drop
/etc/profile.d/go-path.sh so Go stays on PATH in future shells, not
just within the running install script.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/install.sh

@@ -3,6 +3,8 @@
 # built at ./wireguard-ui-multi (run `go build ./cmd/wireguard-ui-multi` first).
 set -euo pipefail
 
+export PATH="/usr/local/go/bin:/usr/local/bin:$PATH"
+
 BIN_SRC="./wireguard-ui-multi"
 BIN_DST="/usr/local/bin/wireguard-ui-multi"
 CONFIG_DIR="/etc/wireguard-ui-multi"
@@ -28,6 +30,12 @@ if [[ ! -f "$BIN_SRC" ]]; then
 	fi
 fi
 
+if [[ -d /usr/local/go/bin ]] && [[ ! -f /etc/profile.d/go-path.sh ]]; then
+	echo "Persisting Go on PATH for future shells (/etc/profile.d/go-path.sh)..."
+	echo 'export PATH="/usr/local/go/bin:$PATH"' > /etc/profile.d/go-path.sh
+	chmod 0644 /etc/profile.d/go-path.sh
+fi
+
 echo "Creating directories..."
 mkdir -p /usr/local/bin
 mkdir -p "$CONFIG_DIR"