Update appcast.xml for version 1.5.1 release

Author: mblackmon

appcast.xml

@@ -4,6 +4,39 @@
         <title>WorkTreeBuddy</title>
         <description>Updates for WorkTreeBuddy</description>
         <language>en</language>
+        <item>
+            <title>Version 1.5.1</title>
+            <pubDate>Fri, 12 Sep 2025 14:29:21 +0000</pubDate>
+            <sparkle:version>18</sparkle:version>
+            <sparkle:shortVersionString>1.5.1</sparkle:shortVersionString>
+            <description><![CDATA[
+            
+            ### Changed
+            - Replaced Refresh button with Settings button in main UI
+            - Settings button now properly opens preferences window with hover effects
+            
+            ]]></description>
+            <enclosure url="https://github.com/oreillymedia/worktreebuddy/releases/download/v1.5.1/WorkTreeBuddy.dmg"
+                       type="application/octet-stream"
+                       length="3097772"
+                       sparkle:edSignature="uDumBlo8Smi8T6glvm1v3cb5gnL+EuZBPJ3NTwxon9RzetldPFLYoma4f/biWyoEHXK+ti/32jR6pN4x/1V8Dw==" />
+        </item>
+        <item>
+            <title>Version 1.5.0</title>
+            <pubDate>Fri, 12 Sep 2025 14:27:26 +0000</pubDate>
+            <sparkle:version>18</sparkle:version>
+            <sparkle:shortVersionString>1.5.0</sparkle:shortVersionString>
+            <description><![CDATA[
+            
+            ### Changed
+            - UI and performance improvements
+            
+            ]]></description>
+            <enclosure url="https://github.com/oreillymedia/worktreebuddy/releases/download/v1.5.0/WorkTreeBuddy.dmg"
+                       type="application/octet-stream"
+                       length="3101560"
+                       sparkle:edSignature="Me/WUkWuCeJRrYzG3ZiAyrRJI3D+kEYjisIps0fia4JkIjCduNlu/UOgJJouaPN68uY0GfEXlVozlUQAMUROCg==" />
+        </item>
         <item>
             <title>Version 1.5.0</title>
             <pubDate>Thu, 11 Sep 2025 14:49:26 +0000</pubDate>