Implement custom 5-color design system across entire iOS app

Apply consistent branding colors (BlueGreen, Cerulean, BrightAmber, PrimaryScarlet,
cream backgrounds) to all screens, components, buttons, icons, and text throughout
the app. Update all Form/List views with proper list row backgrounds to ensure
visual consistency with card-based layouts.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

iosApp/iosApp/MainTabView.swift

@@ -51,6 +51,7 @@ struct MainTabView: View {
             .tag(4)
             .accessibilityIdentifier(AccessibilityIdentifiers.Navigation.profileTab)
         }
+        .tint(Color.appPrimary)
         .onChange(of: authManager.isAuthenticated) { _ in
             selectedTab = 0
         }