add UserDefaults-backed Settings storage

Settings enum holds all upcoming settings-window preferences. Booleans
default to false (disabled by default); includeGreedyCasks and
confirmBeforeUpgradeAll default to true via register(defaults:), which
provides fallbacks without writing to disk. Launch-at-login is not
stored here — SMAppService will be its source of truth.

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

BrewBar/BrewBarApp.swift

@@ -43,6 +43,8 @@ class AppDelegate: NSObject, NSApplicationDelegate {
     // MARK: - Menu
 
     func applicationDidFinishLaunching(_: Notification) {
+        Settings.registerDefaults()
+
         statusItem = NSStatusBar.system.statusItem(withLength: NSStatusItem.variableLength)
         setMenuBarIcon("brewbar-uptodate")
 

BrewBar/Settings.swift

@@ -0,0 +1,47 @@
+import Foundation
+
+/// UserDefaults-backed app settings. Booleans read false for unset keys,
+/// which covers the disabled-by-default settings; enabled-by-default ones
+/// get their fallback via registerDefaults() (consulted only when the user
+/// has never changed the value — nothing is written to disk).
+///
+/// Launch-at-login is intentionally absent: SMAppService is its source of
+/// truth, so storing a copy here could only drift out of sync.
+enum Settings {
+    static func registerDefaults() {
+        UserDefaults.standard.register(defaults: [
+            "includeGreedyCasks": true,
+            "confirmBeforeUpgradeAll": true,
+        ])
+    }
+
+    static var autoUpgradeFormulae: Bool {
+        get { UserDefaults.standard.bool(forKey: "autoUpgradeFormulae") }
+        set { UserDefaults.standard.set(newValue, forKey: "autoUpgradeFormulae") }
+    }
+
+    static var autoUpgradeCasks: Bool {
+        get { UserDefaults.standard.bool(forKey: "autoUpgradeCasks") }
+        set { UserDefaults.standard.set(newValue, forKey: "autoUpgradeCasks") }
+    }
+
+    static var notifyOnNewUpdates: Bool {
+        get { UserDefaults.standard.bool(forKey: "notifyOnNewUpdates") }
+        set { UserDefaults.standard.set(newValue, forKey: "notifyOnNewUpdates") }
+    }
+
+    static var showCountInMenuBar: Bool {
+        get { UserDefaults.standard.bool(forKey: "showCountInMenuBar") }
+        set { UserDefaults.standard.set(newValue, forKey: "showCountInMenuBar") }
+    }
+
+    static var includeGreedyCasks: Bool {
+        get { UserDefaults.standard.bool(forKey: "includeGreedyCasks") }
+        set { UserDefaults.standard.set(newValue, forKey: "includeGreedyCasks") }
+    }
+
+    static var confirmBeforeUpgradeAll: Bool {
+        get { UserDefaults.standard.bool(forKey: "confirmBeforeUpgradeAll") }
+        set { UserDefaults.standard.set(newValue, forKey: "confirmBeforeUpgradeAll") }
+    }
+}