feat(gui): add OriginSelectorWidget for file origin selection (#13)

- Create OriginSelectorWidget class (QToolButton with dropdown menu)
- Add OriginSelectorAction to create widget in toolbars
- Add Std_Origin command registered in CommandStd.cpp
- Add widget to File toolbar (before New/Open/Save)
- Connect to OriginManager fastsignals for origin changes
- Add Catppuccin Mocha styling for the widget
- Widget shows current origin name/icon with connection status overlay

This implements Issue #13: Origin selector toolbar widget

src/Gui/PreferencePacks/KindredCreate/KindredCreate.qss

@@ -1142,6 +1142,28 @@ Gui--WorkbenchComboBox::drop-down {
     border-radius: 0 4px 4px 0;
 }
 
+/* Origin Selector */
+Gui--OriginSelectorWidget {
+    background-color: #313244;
+    color: #cdd6f4;
+    border: 1px solid #45475a;
+    border-radius: 4px;
+    padding: 4px 8px;
+    min-width: 70px;
+    max-width: 120px;
+}
+
+Gui--OriginSelectorWidget:hover {
+    border-color: #585b70;
+    background-color: #45475a;
+}
+
+Gui--OriginSelectorWidget::menu-indicator {
+    subcontrol-origin: padding;
+    subcontrol-position: center right;
+    right: 4px;
+}
+
 /* Task Panel */
 QSint--ActionGroup {
     background-color: #313244;