feat: macOS architecture, cloud ASR/LLM providers, and 6-step iOS onboarding

- Add macOS menu-bar dictation app with local ASR models (SenseVoice/Qwen3),
  global Option hotkey, and bottom overlay
- Add cloud ASR/LLM providers (Anthropic, Volcengine, Bailian, and more) with
  provider logos, model listing, and connection checks
- Add shared 7-day usage stats UI (UsageStatsCluster / SevenDayUsageChart)
- Add iOS onboarding step 6 for polish LLM setup; hide custom-language-model
  diagnostic toggle behind DEBUG
- Unify iOS onboarding tagline with the macOS brand line ("开口即文字。")
- Rewrite README (Chinese-first, product-oriented) and refresh GitHub Pages

OSGKeyboardMac/MacDictationPipeline.swift

@@ -40,7 +40,8 @@ enum MacDictationPipeline {
     /// Whether the active engine can surface `onPartial` text while recording.
     static func supportsLivePartials(store: AppGroupStore) -> Bool {
         if store.engineMode == "local" { return true }
-        return CloudASRModelCatalog.strategy(for: store.asrProviderId) != .localFallback
+        let strategy = CloudASRModelCatalog.strategy(for: store.asrProviderId)
+        return strategy != .localFallback
     }
 
     /// Runs ASR then polish. Polish failures return cleaned raw ASR plus a warning.