Add CampusNAS menu bar agent

Native macOS agent that keeps the office VPN and the NAS shares working
without the shell wrapper it replaces.

- VPN: full port of the `ovpn` script — host-route pinning, gateway
  discovery via networksetup, tunnel liveness by address plus pushed
  route, startup grace, restart of a wedged daemon. Root steps are
  batched into one system authorization prompt.
- SMB: mounts via NetFS, discovers shares from the server, detects
  mounts event-driven through NSWorkspace, matches the host by resolved
  alias so externally created mounts are recognised.
- Credentials never pass through the process: the VPN auth file is
  written by `security` straight to disk, and the password is stored via
  SecItemAdd rather than a command line visible in ps.
- UI: status window, settings editor, ⌘+/⌘− zoom that re-lays out rather
  than scaling a bitmap.

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

Sources/CampusNASMonitor/Main.swift

@@ -0,0 +1,14 @@
+import AppKit
+
+@main
+enum Main {
+    @MainActor
+    static func main() {
+        let app = NSApplication.shared
+        let delegate = AppDelegate()
+        app.delegate = delegate
+        // Menu bar only — no Dock icon, no main window.
+        app.setActivationPolicy(.accessory)
+        app.run()
+    }
+}