feat: TypeWhisper Flow sessions, Phase 4 UX, and GitHub Pages privacy site

Migrate keyboard dictation to continuous Flow sessions with auto-start,
tap-to-toggle recording, 60s countdown, five-step onboarding, and App Group
IPC. Add docs/ GitHub Pages site with en/zh privacy policy for App Store compliance.

OSGKeyboardShared/Services/KeyboardState.swift

@@ -67,6 +67,8 @@ public final class KeyboardState: ObservableObject {
     /// `true` — kept on the state object because the UI's status
     /// badge still wants a single source of truth to read from.
     @Published public var onDeviceSupported: Bool = false
+    /// Seconds remaining in the current utterance (Flow tap-to-talk).
+    @Published public var utteranceRemainingSeconds: Int = Int(FlowSessionKeys.maxUtteranceDuration)
     /// "local" → ASR only, no LLM. "cloud" → ASR + optional LLM polish.
     @Published public var engineMode: String = "cloud"