Add bterminal icon to installer and desktop entry

The SVG icon was installed locally but missing from the repo.
Installer now copies it to ~/.local/share/icons/ and desktop
entry uses the correct icon name.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bterminal.svg

@@ -0,0 +1,19 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 128 128">
+  <defs>
+    <linearGradient id="bg" x1="0" y1="0" x2="0" y2="1">
+      <stop offset="0%" stop-color="#313244"/>
+      <stop offset="100%" stop-color="#1e1e2e"/>
+    </linearGradient>
+  </defs>
+  <!-- Rounded background -->
+  <rect x="4" y="4" width="120" height="120" rx="24" ry="24" fill="url(#bg)" stroke="#45475a" stroke-width="2"/>
+  <!-- Terminal prompt chevron > -->
+  <polyline points="30,48 54,64 30,80" fill="none" stroke="#a6e3a1" stroke-width="8" stroke-linecap="round" stroke-linejoin="round"/>
+  <!-- Cursor/underscore -->
+  <line x1="62" y1="80" x2="98" y2="80" stroke="#89b4fa" stroke-width="8" stroke-linecap="round"/>
+  <!-- SSH key icon (small, top-right corner) -->
+  <circle cx="96" cy="36" r="8" fill="none" stroke="#f9e2af" stroke-width="3"/>
+  <line x1="96" y1="44" x2="96" y2="56" stroke="#f9e2af" stroke-width="3" stroke-linecap="round"/>
+  <line x1="96" y1="50" x2="102" y2="50" stroke="#f9e2af" stroke-width="3" stroke-linecap="round"/>
+  <line x1="96" y1="56" x2="102" y2="56" stroke="#f9e2af" stroke-width="3" stroke-linecap="round"/>
+</svg>