fix: [M3-7260] - Managed Summary layout (#10042)

## Description 📝
Fix loading and dark mode styling for the Managed Summary tab

## How to test 🧪

### Prerequisites
(How to setup test environment)
- Have an account that's Managed (you can do so via admin)

### Verification steps 
(How to verify changes)
-  Go to `/managed/summary`, there should no longer be a styling loading blip.
- The container background in dark mode should now match the graph.

packages/manager/.changeset/pr-10042-fixed-1704748141170.md

@@ -0,0 +1,5 @@
+---
+"@linode/manager": Fixed
+---
+
+Managed Summary layout ([#10042](https://github.com/linode/manager/pull/10042))

packages/manager/src/features/Managed/ManagedDashboardCard/ManagedChartPanel.styles.tsx

@@ -29,6 +29,9 @@ export const StyledGraphControlsDiv = styled('div', {
     top: 52,
     width: 1,
   },
+  alignItems: 'center',
+  display: 'flex',
+  minHeight: 460,
   position: 'relative',
   [theme.breakpoints.up('sm')]: {
     width: '60%',

packages/manager/src/features/Managed/ManagedDashboardCard/ManagedChartPanel.tsx

@@ -275,7 +275,11 @@ export const ManagedChartPanel = () => {
   }
 
   if (isLoading) {
-    return <CircleProgress />;
+    return (
+      <StyledGraphControlsDiv>
+        <CircleProgress />
+      </StyledGraphControlsDiv>
+    );
   }
 
   if (!data) {

packages/manager/src/features/Managed/ManagedDashboardCard/ManagedDashboardCard.styles.tsx

@@ -15,8 +15,11 @@ export const StyledMonitorStatusOuterGrid = styled(Grid, {
 export const StyledOuterContainerGrid = styled(Grid, {
   label: 'StyledOuterContainerGrid',
 })(({ theme }) => ({
+  background: theme.bg.bgPaper,
+  flexDirection: 'column',
   margin: '-8px',
   [theme.breakpoints.up('sm')]: {
+    flexDirection: 'row',
     flexWrap: 'nowrap',
     justifyContent: 'space-evenly',
   },