feat: create dedicated desktop dock icon and update nix build to use it

- Add app/sovran_systemsos_web/static/sovran-hub-icon.svg: a new square
  256x256 app icon for the GNOME dock/dash. Uses the Sovran brand dark
  green (#0d3320) rounded-rectangle background, concentric arc rings in
  brand greens (#1C9954, #077233), and a white bold "S" letterform
  centered — visible at small sizes on both light and dark panels.
- Update modules/core/sovran-hub.nix line 266 to copy the new icon file
  to the hicolor icon path instead of reusing logo-light.svg.
- logo-light.svg is left untouched; it continues to serve the Hub web UI.

Agent-Logs-Url: https://github.com/naturallaw777/staging_alpha/sessions/e3f466ae-eee1-4ba8-b93c-00fe04c7054d

Co-authored-by: naturallaw777 <99053422+naturallaw777@users.noreply.github.com>

app/sovran_systemsos_web/static/sovran-hub-icon.svg

@@ -0,0 +1,16 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" width="256" height="256">
+  <!-- Rounded rectangle background using Sovran brand dark green -->
+  <rect width="256" height="256" rx="48" ry="48" fill="#0d3320"/>
+
+  <!-- Outer arc ring (brand green #1C9954) -->
+  <path d="M 128,40 A 88,88 0 1 1 56.8,183.2" fill="none" stroke="#1C9954" stroke-width="14" stroke-linecap="round"/>
+
+  <!-- Middle arc ring (darker brand green #077233) -->
+  <path d="M 128,60 A 68,68 0 1 1 74.8,176.4" fill="none" stroke="#077233" stroke-width="10" stroke-linecap="round"/>
+
+  <!-- Inner arc ring (lighter green for depth) -->
+  <path d="M 128,80 A 48,48 0 1 1 93.1,169.8" fill="none" stroke="#1C9954" stroke-width="8" stroke-linecap="round"/>
+
+  <!-- White "S" letterform centered -->
+  <text x="128" y="152" font-family="sans-serif" font-weight="bold" font-size="88" text-anchor="middle" fill="#ffffff" opacity="0.95">S</text>
+</svg>

modules/core/sovran-hub.nix

@@ -263,7 +263,7 @@ let
       cp icons/* $out/share/sovran-hub/icons/ 2>/dev/null || true
 
       install -d $out/share/icons/hicolor/scalable/apps
-      cp sovran_systemsos_web/static/logo-light.svg $out/share/icons/hicolor/scalable/apps/sovran-hub.svg
+      cp sovran_systemsos_web/static/sovran-hub-icon.svg $out/share/icons/hicolor/scalable/apps/sovran-hub.svg
 
       install -d $out/share/applications
       cat > $out/share/applications/sovran-hub.desktop <<DESKTOP