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>

Core/Models/NASConnection.swift

@@ -10,6 +10,8 @@ enum NASProtocol: String, Codable, CaseIterable {
         case .sftp: return 22
         }
     }
+
+    var localizedDescription: String { rawValue }
 }
 
 struct NASConnection: Codable, Identifiable, Equatable {
@@ -18,10 +20,15 @@ struct NASConnection: Codable, Identifiable, Equatable {
     var port: Int
     var nasProtocol: NASProtocol
     var username: String
-    var password: String
+    var password: String   // Runtime only — persisted in Keychain, not UserDefaults
     var remotePath: String
     var displayName: String
 
+    // Excludes password so it is never written to UserDefaults.
+    enum CodingKeys: String, CodingKey {
+        case id, host, port, nasProtocol, username, remotePath, displayName
+    }
+
     init(
         host: String,
         port: Int? = nil,
@@ -39,4 +46,16 @@ struct NASConnection: Codable, Identifiable, Equatable {
         self.remotePath = remotePath
         self.displayName = displayName.isEmpty ? host : displayName
     }
+
+    init(from decoder: Decoder) throws {
+        let c = try decoder.container(keyedBy: CodingKeys.self)
+        id          = try c.decode(UUID.self,        forKey: .id)
+        host        = try c.decode(String.self,      forKey: .host)
+        port        = try c.decode(Int.self,         forKey: .port)
+        nasProtocol = try c.decode(NASProtocol.self, forKey: .nasProtocol)
+        username    = try c.decode(String.self,      forKey: .username)
+        remotePath  = try c.decode(String.self,      forKey: .remotePath)
+        displayName = try c.decode(String.self,      forKey: .displayName)
+        password    = ""  // filled from Keychain by SavedConnections.load()
+    }
 }