Add Last Seen column and color-coded status badges in Machines table

- New Last Seen column showing last_seen_at timestamp per machine
- Status badges: online=green (success), offline=red (error), waking/pending=amber
- Update Machine interface with last_seen_at and created_at fields

web/src/lib/status.ts

@@ -25,7 +25,7 @@ export type BadgeVariant = VariantProps<typeof badgeVariants>['variant']
 const STATUS_TO_VARIANT: Record<string, BadgeVariant> = {
   running: 'running',
   pending: 'pending',
-  waking: 'waking',
+  waking: 'pending',
   success: 'success',
   error: 'error',
   failed: 'error',
@@ -33,6 +33,8 @@ const STATUS_TO_VARIANT: Record<string, BadgeVariant> = {
   cancelled: 'neutral',
   info: 'info',
   unknown: 'neutral',
+  online: 'success',
+  offline: 'error',
 }
 
 export function statusVariant(status: string): BadgeVariant {