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

OSGKeyboardShared/Services/AppGroupStore.swift

@@ -66,6 +66,7 @@ public struct AppGroupStore: @unchecked Sendable {
     public var handednessPreference: HandednessPreference { configuration.handednessPreference }
     public var cursorDragNavigationEnabled: Bool { configuration.cursorDragNavigationEnabled }
     public var polishIntensity: PolishIntensity { configuration.polishIntensity }
+    public var llmThinkingEnabled: Bool { configuration.llmThinkingEnabled }
     public var isTranslationEffective: Bool { configuration.isTranslationEffective }
     public var isLocalEngine: Bool { configuration.isLocalEngine }
     public var polishModeForPipeline: PolishingService.PolishMode { configuration.polishModeForPipeline }
@@ -87,21 +88,7 @@ public struct AppGroupStore: @unchecked Sendable {
     }
 
     public func setEngineMode(_ mode: String) {
-        mutateConfiguration { config in
-            config.engineMode = mode
-            if mode == "cloud", config.providerId == "deepseek" {
-                let openAI = LLMProvider.provider(id: "openai")
-                config.providerId = openAI.id
-                config.baseURL = openAI.defaultBaseURL
-                config.model = openAI.defaultModel
-            }
-            if mode == "cloud", config.asrProviderId == "deepseek" {
-                let openAI = LLMProvider.provider(id: "openai")
-                config.asrProviderId = openAI.id
-                config.asrBaseURL = openAI.defaultBaseURL
-                config.asrModel = CloudASRModelCatalog.defaultModel(for: openAI.id)
-            }
-        }
+        mutateConfiguration { $0.engineMode = mode }
         AppGroupConfigDarwin.postConfigChanged()
     }
 
@@ -134,6 +121,11 @@ public struct AppGroupStore: @unchecked Sendable {
         mutateConfiguration { $0.polishIntensity = intensity }
     }
 
+    public func setLLMThinkingEnabled(_ enabled: Bool) {
+        mutateConfiguration { $0.llmThinkingEnabled = enabled }
+        AppGroupConfigDarwin.postConfigChanged()
+    }
+
     public func setLocalASRCustomLanguageModelEnabled(_ enabled: Bool) {
         mutateConfiguration { $0.localASRCustomLanguageModelEnabled = enabled }
     }