build: update stable appcast release URL

appcast.xml

@@ -38,6 +38,7 @@
 <li>iOS/App Store Connect release prep: align iOS bundle identifiers under <code>ai.openclaw.client</code>, refresh Watch app icons, add Fastlane metadata/screenshot automation, and support Keychain-backed ASC auth for uploads. (#38936) Thanks @ngutman.</li>
 <li>Mattermost/model picker: add Telegram-style interactive provider/model browsing for <code>/oc_model</code> and <code>/oc_models</code>, fix picker callback updates, and emit a normal confirmation reply when a model is selected. (#38767) thanks @mukhtharcm.</li>
 <li>Docker/multi-stage build: restructure Dockerfile as a multi-stage build to produce a minimal runtime image without build tools, source code, or Bun; add <code>OPENCLAW_VARIANT=slim</code> build arg for a bookworm-slim variant. (#38479) Thanks @sallyom.</li>
+<li>Google/Gemini 3.1 Flash-Lite: add first-class <code>google/gemini-3.1-flash-lite-preview</code> support across model-id normalization, default aliases, media-understanding image lookups, Google Gemini CLI forward-compat fallback, and docs.</li>
 </ul>
 <h3>Breaking</h3>
 <ul>
@@ -361,7 +362,7 @@
 </ul>
 <p><a href="https://github.com/openclaw/openclaw/blob/main/CHANGELOG.md">View full changelog</a></p>
 ]]></description>
-            <enclosure url="https://github.com/openclaw/openclaw/releases/download/v2026.3.7-beta.1/OpenClaw-2026.3.7.zip" length="23263836" type="application/octet-stream" sparkle:edSignature="IjhLPw9QKZukMDV0rU/06N2D0cu7WyNBPfZ+UL58KbTo7av7s3syYAGAmr+zhvfkMoqvtrQfN9prnvnNIKLNCQ=="/>
+            <enclosure url="https://github.com/openclaw/openclaw/releases/download/v2026.3.7/OpenClaw-2026.3.7.zip" length="23263833" type="application/octet-stream" sparkle:edSignature="SO0zedZMzrvSDltLkuaSVQTWFPPPe1iu/enS4TGGb5EGckhqRCmNJWMKNID5lKwFC8vefTbfG9JTlSrZedP4Bg=="/>
         </item>
         <item>
             <title>2026.3.2</title>