feat: iOS appearance, iPad logo fix, demo seed, and landing hero polish

Add System/Light/Dark preference for iPhone and iPad, restore the iPad
sidebar brand mark, ship a DEBUG seed-demo URL for rich placeholder data,
and refresh GitHub Pages with the device composite, full-bleed pale-green
hero wash, and transparent Mac screenshot chrome.

OSGKeyboardMac/Info.plist

@@ -23,6 +23,17 @@
 	<string>APPL</string>
 	<key>CFBundleShortVersionString</key>
 	<string>$(MARKETING_VERSION)</string>
+	<key>CFBundleURLTypes</key>
+	<array>
+		<dict>
+			<key>CFBundleURLName</key>
+			<string>com.osgkeyboard.mac.seed</string>
+			<key>CFBundleURLSchemes</key>
+			<array>
+				<string>osgkeyboard</string>
+			</array>
+		</dict>
+	</array>
 	<key>CFBundleVersion</key>
 	<string>$(CURRENT_PROJECT_VERSION)</string>
 	<key>ITSAppUsesNonExemptEncryption</key>

OSGKeyboardMac/OSGKeyboardMacApp.swift

@@ -52,6 +52,20 @@ struct OSGKeyboardMacApp: App {
                 .onReceive(NotificationCenter.default.publisher(for: .speechHistoryDidSyncFromCloud)) { _ in
                     viewModel.speechHistory.reloadFromDisk()
                 }
+                .onOpenURL { url in
+                    #if DEBUG
+                    guard url.scheme == "osgkeyboard", url.host == "seed-demo" else { return }
+                    DemoDataSeeder.seedRichPlaceholderData(
+                        defaults: .standard,
+                        historyDefaults: .standard
+                    )
+                    viewModel.reloadConfigFromCloud()
+                    viewModel.refreshDictionaryFromCloud()
+                    viewModel.usageStatistics.reloadFromDisk()
+                    viewModel.speechHistory.reloadFromDisk()
+                    hasCompletedMacOnboarding = true
+                    #endif
+                }
         }
         // Borderless titlebar → content (sidebar + traffic lights) runs to the
         // very top, matching macOS System Settings.