make app icon url not required, swap change theme button icons, fix loading spinners render, add loading state to submit button on create page

src/shared/LoadingSpinner/LoadingSpinner.tsx

@@ -0,0 +1,17 @@
+import { CircularProgress, CircularProgressProps, styled } from '@mui/material'
+import { FC } from 'react'
+
+type LoadingSpinnerProps = CircularProgressProps & {
+  mode?: 'default' | 'secondary'
+}
+
+export const LoadingSpinner: FC<LoadingSpinnerProps> = (props) => {
+  return <StyledCircularProgress {...props} />
+}
+
+export const StyledCircularProgress = styled((props: LoadingSpinnerProps) => (
+  <CircularProgress size={'1rem'} {...props} />
+))(({ theme, mode = 'default' }) => ({
+  marginLeft: '0.5rem',
+  color: mode === 'default' ? theme.palette.text.secondary : theme.palette.text.primary,
+}))