Move variant argument to last position in Container

Ensure consistent argument ordering: layout/components/controls first,
then variant last for all vm.Container definitions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app.py

@@ -155,7 +155,6 @@ regions_page = vm.Page(
             layout=vm.Grid(grid=[[0, 1]]),
             components=[
                 vm.Container(
-                    variant="filled",
                     components=[
                         vm.Graph(
                             id="region_map_chart",
@@ -164,6 +163,7 @@ regions_page = vm.Page(
                             actions=va.set_control(control="state_filter", value="State_Code")
                         )
                     ],
+                    variant="filled"
                 ),
                 vm.Container(
                     controls=[