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/Extensions/Date+.swift

@@ -0,0 +1,30 @@
+import Foundation
+
+extension Date {
+    private static let friendlyFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateStyle = .medium
+        f.timeStyle = .short
+        return f
+    }()
+
+    private static let relativeFormatter: RelativeDateTimeFormatter = {
+        let f = RelativeDateTimeFormatter()
+        f.unitsStyle = .abbreviated
+        return f
+    }()
+
+    var friendlyString: String {
+        Date.friendlyFormatter.string(from: self)
+    }
+
+    var relativeString: String {
+        Date.relativeFormatter.localizedString(for: self, relativeTo: Date())
+    }
+
+    var backupTimestamp: String {
+        let f = DateFormatter()
+        f.dateFormat = "yyyyMMdd_HHmmss"
+        return f.string(from: self)
+    }
+}