fix(dashboard): drop the border around the footer folder toggle

The status-bar folder-toggle button had a 1px border + radius that made it
look like a chip. Per request, render it as a bare icon — transparent
background, no border. Hover now only shifts the icon color, the active
state drops to color only, and focus-visible still draws a focus ring with
border-radius applied so it remains a clean halo.

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

packages/dashboard/app/components/CustomModelDropdown.tsx

@@ -522,8 +522,12 @@ export function CustomModelDropdown({
                   role="option"
                   aria-selected={isSelected}
                 >
-                  <ProviderIcon provider={model.provider} size="sm" />
-                  <span className="model-combobox-option-text">{model.name}</span>
+                  <span className="model-combobox-option-main">
+                    <span className="model-combobox-option-icon">
+                      <ProviderIcon provider={model.provider} size="sm" />
+                    </span>
+                    <span className="model-combobox-option-text">{model.name}</span>
+                  </span>
                   <span className="model-combobox-option-id">{model.id}</span>
                   {onToggleModelFavorite && (
                     <button