feat(zsh): add nbup with progress bar and drop Intel branch

zsh/.config/zsh/config/netbird.zsh

@@ -0,0 +1,31 @@
+#!/usr/bin/env zsh
+
+# NetBird is installed from the official signed .pkg, not Homebrew: the brew
+# cask removed the launchd plist in uninstall_preflight and then ran the app's
+# installer.sh against the missing service, leaving the daemon crash-looping.
+# The pkg's preinstall aborts if the brew formula is present, so keep it out.
+nbup() {
+    local pkg tmp
+    tmp="$(mktemp -d)" || return 1
+    pkg="$tmp/netbird.pkg"
+
+    print "netbird: downloading arm64 pkg"
+    curl -fL --progress-bar -o "$pkg" "https://pkgs.netbird.io/macos/arm64" || { rm -rf "${tmp:?}"; return 1; }
+
+    if ! pkgutil --check-signature "$pkg" | grep -q "NetBird GmbH"; then
+        print -u2 "netbird: unexpected pkg signature, refusing to install"
+        rm -rf "${tmp:?}"
+        return 1
+    fi
+
+    sudo installer -pkg "$pkg" -target / || { rm -rf "${tmp:?}"; return 1; }
+    rm -rf "${tmp:?}"
+
+    local i
+    for i in {1..30}; do
+        [[ -S /var/run/netbird.sock ]] && break
+        sleep 1
+    done
+    /usr/local/bin/netbird status 2>/dev/null |
+        grep -E '^(Daemon version|CLI version|Management|Signal|NetBird IP):'
+}