feat: Kisani rebrand, step-based onboarding flow, dark mode fixes

- Rename app to Kisani in all UI text and Face ID prompt
- Replace flat 2-state RootView with 5-step flow: ConnectView →
  LoginView → FolderSetupView → PhotoPermissionView → MainTabView
- Remove NavigationStack from LoginView (was causing nested-stack crash);
  drive navigation via ConnectionStore.isSessionActive
- Add FolderSetupView and PhotoPermissionView onboarding screens with
  step indicator (2/3, 3/3), spring entrance animations, and UGreen
  connection chip
- Fix dark mode button invisibility: PrimaryButtonStyle and PillButtonStyle
  now use AppTheme.inkInverse; GhostButtonStyle border uses ink.opacity(0.25)
- Add AppTheme.inkInverse adaptive token (dark bg ink on dark, white on light)
- Add ConnectionStore.isSessionActive (non-persisted) and
  onboardingPhotoShown (UserDefaults-persisted)
- Add os_log logging in LoginViewModel at auth start/success/failure
- Remove dead Help button from ConnectView
- UGreenCompatibilityBadge, KeychainStore, SavedConnections, extensions,
  PrivacyInfo.xcprivacy, unit test target and test stubs
- AppTheme: full UIColor dynamic provider tokens for dark/light adaptive color
- AppearanceMode enum + segmented picker in SettingsView
- BackupView: enlarged ring, removed options card and linear progress bar
- HistoryView: duration and bytes formatting, improved typography hierarchy

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

Shared/Persistence/ConnectionStore.swift

@@ -15,7 +15,10 @@ final class ConnectionStore: ObservableObject {
     static let shared = ConnectionStore()
 
     @Published var savedConnection: NASConnection? {
-        didSet { saveUD(savedConnection, key: "savedConnection") }
+        didSet {
+            if let conn = savedConnection { SavedConnections.save(conn) }
+            else { SavedConnections.delete() }
+        }
     }
     @Published var backupFilter: BackupFilter {
         didSet { saveUD(backupFilter, key: "backupFilter") }
@@ -42,6 +45,19 @@ final class ConnectionStore: ObservableObject {
         didSet { UserDefaults.standard.set(quietHoursEnd, forKey: "quietHoursEnd") }
     }
 
+    // Session — not persisted, resets on every app launch
+    @Published var isSessionActive = false
+
+    // Onboarding — persisted so we only show each step once
+    @Published var onboardingPhotoShown: Bool {
+        didSet { UserDefaults.standard.set(onboardingPhotoShown, forKey: "onboardingPhotoShown") }
+    }
+
+    // Appearance
+    @Published var appearanceMode: AppearanceMode {
+        didSet { UserDefaults.standard.set(appearanceMode.rawValue, forKey: "appearanceMode") }
+    }
+
     // Cellular & remote access
     @Published var allowCellularBackup: Bool {
         didSet { UserDefaults.standard.set(allowCellularBackup, forKey: "allowCellularBackup") }
@@ -56,7 +72,7 @@ final class ConnectionStore: ObservableObject {
     @Published private(set) var historyEntries: [BackupHistoryEntry] = []
 
     private init() {
-        savedConnection        = ud(NASConnection.self, key: "savedConnection")
+        savedConnection        = SavedConnections.load()
         backupFilter           = ud(BackupFilter.self, key: "backupFilter") ?? BackupFilter()
         trustedSSIDs           = UserDefaults.standard.stringArray(forKey: "trustedSSIDs") ?? []
         lanTriggerEnabled      = UserDefaults.standard.object(forKey: "lanTriggerEnabled") as? Bool ?? true
@@ -65,6 +81,8 @@ final class ConnectionStore: ObservableObject {
         quietHoursEnabled      = UserDefaults.standard.object(forKey: "quietHoursEnabled") as? Bool ?? false
         quietHoursStart        = UserDefaults.standard.object(forKey: "quietHoursStart") as? Int ?? 23
         quietHoursEnd          = UserDefaults.standard.object(forKey: "quietHoursEnd") as? Int ?? 7
+        onboardingPhotoShown   = UserDefaults.standard.bool(forKey: "onboardingPhotoShown")
+        appearanceMode         = AppearanceMode(rawValue: UserDefaults.standard.string(forKey: "appearanceMode") ?? "") ?? .system
         allowCellularBackup    = UserDefaults.standard.object(forKey: "allowCellularBackup") as? Bool ?? false
         useTailscaleWhenRemote = UserDefaults.standard.object(forKey: "useTailscaleWhenRemote") as? Bool ?? false
         tailscaleHost          = UserDefaults.standard.string(forKey: "tailscaleHost") ?? ""