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>

Features/Login/LoginViewModel.swift

@@ -1,5 +1,6 @@
 import Foundation
 import LocalAuthentication
+import os.log
 
 @MainActor
 final class LoginViewModel: ObservableObject {
@@ -9,26 +10,34 @@ final class LoginViewModel: ObservableObject {
 
     var onAuthenticated: (() -> Void)?
 
+    private let logger = Logger(subsystem: "com.albert.nasbackup", category: "Login")
+
     func authenticateWithFaceID() {
+        logger.info("Face ID authentication started")
         isAuthenticating = true
         authError = nil
         let context = LAContext()
         var error: NSError?
         guard context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) else {
+            let reason = error?.localizedDescription ?? "unknown"
+            logger.error("Face ID not available: \(reason, privacy: .public)")
             authError = "Face ID not available"
             isAuthenticating = false
             return
         }
         context.evaluatePolicy(
             .deviceOwnerAuthenticationWithBiometrics,
-            localizedReason: "Sign in to NASBackup"
+            localizedReason: "Sign in to Kisani"
         ) { [weak self] success, evalError in
             Task { @MainActor in
                 self?.isAuthenticating = false
                 if success {
+                    self?.logger.info("Face ID authentication succeeded — advancing session")
                     self?.onAuthenticated?()
                 } else {
-                    self?.authError = evalError?.localizedDescription ?? "Authentication failed"
+                    let reason = evalError?.localizedDescription ?? "Authentication failed"
+                    self?.logger.error("Face ID authentication failed: \(reason, privacy: .public)")
+                    self?.authError = reason
                 }
             }
         }