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

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

src/components/ui/EmptyState.tsx

@@ -15,7 +15,7 @@ export function EmptyState({ icon, title, description, action }: EmptyStateProps
   return (
     <Box className="flex flex-col items-center justify-center gap-3 py-16 px-8 text-center">
       {icon && <Box className="text-slate-400 mb-2">{icon}</Box>}
-      <Typography variant="h6" color="text.primary" fontWeight={500}>{title}</Typography>
+      <Typography variant="h6" color="text.primary" sx={{ fontWeight: 500 }}>{title}</Typography>
       {description && (
         <Typography variant="body2" color="text.secondary" className="max-w-sm">{description}</Typography>
       )}

src/components/ui/SectionContainer.tsx

@@ -16,7 +16,7 @@ export function SectionContainer({ title, subtitle, action, children, className
       {(title || action) && (
         <Box className="flex items-center justify-between gap-2">
           <Box>
-            {title && <Typography variant="subtitle1" fontWeight={600} color="text.primary">{title}</Typography>}
+            {title && <Typography variant="subtitle1" sx={{ fontWeight: 600 }} color="text.primary">{title}</Typography>}
             {subtitle && <Typography variant="caption" color="text.secondary">{subtitle}</Typography>}
           </Box>
           {action}