Phase 3: app icon (multi-resolution ICO + master PNG)

scripts/generate-icons.ps1 renders the icon programmatically with
System.Drawing - rounded teal square (#0E7C66) with a stylized white
hook glyph - at 16/24/32/48/64/128/256 px and assembles a proper
multi-resolution Microsoft ICO. The PNG and ICO outputs land in
resources/. The script is the source of truth; re-run after editing
the design.

GUI csproj uses ApplicationIcon for the EXE icon and embeds the .ico
+ .png as Resources so MainWindow and AboutDialog can use them via
WPF's resource URI scheme.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/WebhookServer.Gui/WebhookServer.Gui.csproj

@@ -14,6 +14,13 @@
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <UseWPF>true</UseWPF>
+    <ApplicationIcon>..\..\resources\webhook-server.ico</ApplicationIcon>
+    <AssemblyTitle>Webhook Server</AssemblyTitle>
   </PropertyGroup>
 
+  <ItemGroup>
+    <Resource Include="..\..\resources\webhook-server.ico" Link="webhook-server.ico" />
+    <Resource Include="..\..\resources\webhook-server.png" Link="webhook-server.png" />
+  </ItemGroup>
+
 </Project>