feat(ui): use the new OpenNest application icon

Set it as the exe's ApplicationIcon and as the main and help windows'
icon (the main window showed the WinForms default). The .ico is
rendered from OpenNest.svg as 32-bit images from 16 to 256 px.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

OpenNest/Forms/MainForm.cs

@@ -109,6 +109,7 @@ namespace OpenNest.Forms
             storage = new NestStorageController(this, text => statusLabel1.Text = text);
             storage.StateChanged += Storage_StateChanged;
             InitializeComponent();
+            Icon = Resources.app_icon;
             statusStrip1.Items.Insert(statusStrip1.Items.IndexOf(materialStatusLabel) + 1, ledgerStatusLabel);
             ledgerStatusLabel.Click += LedgerStatusLabel_Click;
             statusStrip1.ShowItemToolTips = true; // The hold list lives in the ledger label's tooltip.

OpenNest/Help/HelpForm.cs

@@ -33,7 +33,7 @@ namespace OpenNest.Help
         {
             pendingPage = page;
             Text = "OpenNest Help";
-            Icon = Icon.ExtractAssociatedIcon(Application.ExecutablePath);
+            Icon = Properties.Resources.app_icon;
             StartPosition = FormStartPosition.Manual;
             var area = Screen.FromPoint(Cursor.Position).WorkingArea;
             Size = new Size(System.Math.Min(1100, area.Width), System.Math.Min(900, area.Height));

OpenNest/OpenNest.csproj

@@ -6,6 +6,7 @@
     <AssemblyName>OpenNest</AssemblyName>
     <UseWindowsForms>true</UseWindowsForms>
     <ApplicationHighDpiMode>DpiUnaware</ApplicationHighDpiMode>
+    <ApplicationIcon>Resources\OpenNest.ico</ApplicationIcon>
     <Version>0.4.0</Version>
   </PropertyGroup>
   <ItemGroup>

OpenNest/Properties/Resources.Designer.cs

@@ -83,6 +83,13 @@ namespace OpenNest.Properties {
         /// <summary>
         ///   Looks up a localized resource of type System.Drawing.Bitmap.
         /// </summary>
+        internal static System.Drawing.Icon app_icon {
+            get {
+                object obj = ResourceManager.GetObject("app_icon", resourceCulture);
+                return ((System.Drawing.Icon)(obj));
+            }
+        }
+
         internal static System.Drawing.Bitmap cut_planner {
             get {
                 object obj = ResourceManager.GetObject("cut_planner", resourceCulture);

OpenNest/Properties/Resources.resx

@@ -205,4 +205,7 @@
   <data name="drawing_library" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\drawing_library.png;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
+  <data name="app_icon" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\OpenNest.ico;System.Drawing.Icon, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
 </root>

OpenNest/Resources/OpenNest.svg

@@ -0,0 +1,20 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256">
+  <defs>
+    <linearGradient id="bg" x1="0" y1="0" x2="1" y2="1">
+      <stop offset="0" stop-color="#17334a"/>
+      <stop offset="1" stop-color="#0b1826"/>
+    </linearGradient>
+    <linearGradient id="steel" x1="0" y1="0" x2="1" y2="1">
+      <stop offset="0" stop-color="#f4f8fa"/>
+      <stop offset="1" stop-color="#a8c3d3"/>
+    </linearGradient>
+  </defs>
+  <rect x="8" y="8" width="240" height="240" rx="52" fill="url(#bg)"/>
+  <path d="M54 66h148v124H54z" fill="none" stroke="#51d6bd" stroke-width="8" stroke-linejoin="round"/>
+  <path d="M68 82h48v38H68z" fill="url(#steel)"/>
+  <path d="M126 82h60v20h-60zM126 110h60v34h-60z" fill="#67a6c8"/>
+  <path d="M68 132h48v44H68z" fill="#67a6c8"/>
+  <path d="M126 152h60v24h-60z" fill="url(#steel)"/>
+  <path d="M122 62v132" stroke="#f5bf58" stroke-width="5" stroke-linecap="round" stroke-dasharray="2 12"/>
+  <circle cx="122" cy="62" r="8" fill="#f5bf58"/>
+</svg>