chore: adopt source-available license and strengthen privacy disclosures

Replace MIT with a restrictive source-available license and align README/docs copy. Add cloud polish acknowledgment, privacy manifest updates, voice history disclosure, export compliance metadata, and support links for App Store readiness.

docs/index.html

@@ -719,7 +719,7 @@
 
   <footer class="footer">
     <div class="footer-inner">
-      <span data-i18n="footer.copy">© OSGKeyboard — open source under MIT</span>
+      <span data-i18n="footer.copy">© OSGKeyboard — source available</span>
       <span>
         <a href="https://github.com/hkgood/OSGKeyboard" data-i18n="footer.source">Source code</a>
         ·
@@ -732,7 +732,7 @@
     const copy = {
       en: {
         "nav.github": "GitHub",
-        "hero.eyebrow": "Open source · iOS 26+",
+        "hero.eyebrow": "Source available · iOS 26+",
         "hero.title": "Hold to talk.<br>Polished text in any app.",
         "hero.lead": "A custom keyboard that transcribes your voice on-device and optionally polishes the result with the LLM you configure — WeChat, Notes, Mail, ChatGPT, and everywhere else you type.",
         "hero.cta.primary": "View on GitHub",
@@ -768,13 +768,13 @@
         "privacy.title": "Privacy at a glance",
         "privacy.body": "Audio is processed on your device. We do not log ordinary keystrokes. In cloud polish mode, only transcribed text — never audio — goes to the API provider you configure.",
         "privacy.cta": "Read full policy",
-        "footer.copy": "© OSGKeyboard — open source under MIT",
+        "footer.copy": "© OSGKeyboard — source available",
         "footer.source": "Source code",
         "footer.privacy": "Privacy"
       },
       zh: {
         "nav.github": "GitHub",
-        "hero.eyebrow": "开源 · 需要 iOS 26+",
+        "hero.eyebrow": "源码可见 · 需要 iOS 26+",
         "hero.title": "按住说话，<br>任意 App 里获得润色文字。",
         "hero.lead": "自定义键盘扩展：在设备端转写语音，并可选通过你配置的 LLM 润色结果。适用于微信、备忘录、邮件、ChatGPT 等所有出现键盘的场景。",
         "hero.cta.primary": "GitHub 仓库",
@@ -810,7 +810,7 @@
         "privacy.title": "隐私摘要",
         "privacy.body": "音频在设备端处理。我们不记录普通击键。云端润色模式下，仅转写文字（非音频）会发送到你配置的 API 服务商。",
         "privacy.cta": "查看完整政策",
-        "footer.copy": "© OSGKeyboard · MIT 开源",
+        "footer.copy": "© OSGKeyboard · 源码可见",
         "footer.source": "源代码",
         "footer.privacy": "隐私"
       }