fix: TypeScript build errors (TS6 enum → const, MUI v9 sx props, theme)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/theme.ts

@@ -79,9 +79,11 @@ export const theme = createTheme({
       defaultProps: { disableElevation: true },
       styleOverrides: {
         root: { borderRadius: 6, padding: '6px 16px' },
-        containedPrimary: {
-          background: '#1e3a5f',
-          '&:hover': { background: '#142a45' },
+        contained: {
+          '&.MuiButton-containedPrimary': {
+            background: '#1e3a5f',
+            '&:hover': { background: '#142a45' },
+          },
         },
       },
     },