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

.gitignore

@@ -73,3 +73,8 @@ __pycache__/
 
 # Standalone experiment: 灵动岛录音机制验证 demo (throwaway)
 AudioIntentProbe/
+
+# Local crash-log pulls and one-off diff/working notes (not for the repo)
+.crash-pull/
+all-changes-vs-main.patch
+CHANGES.md