release: update appcast for v1.4.0

Author: JerryZLiu

docs/appcast.xml

@@ -3,6 +3,18 @@
   <channel>
     <title>Dayflow Updates</title>
     <language>en</language>
+    <item>
+      <title>Version 1.4.0</title>
+      <pubDate>Tue, 09 Dec 2025 11:02:34 +0000</pubDate>
+      <enclosure url="https://github.com/JerryZLiu/Dayflow/releases/download/v1.4.0/Dayflow.dmg"
+                 sparkle:version="70"
+                 sparkle:shortVersionString="1.4.0"
+                 length="37288191"
+                 type="application/octet-stream"
+                 sparkle:edSignature="dn2wypopeDFqaCKdbMeivVwELFJro1TP3YdJjiiUqMj7USh0JqA6bseFEhXShFpVE6dCRUoZQe55ts4QXacSBg=="/>
+      <sparkle:minimumSystemVersion>13.0</sparkle:minimumSystemVersion>
+      <releaseNotesLink>https://github.com/JerryZLiu/Dayflow/releases/tag/v1.4.0</releaseNotesLink>
+    </item>
     <item>
       <title>Version 1.3.6</title>
       <pubDate>Fri, 05 Dec 2025 10:06:29 +0000</pubDate>