fix(nodes): add disk columns to ListNodes SELECT (scanNodes 37/39 mismatch → 500)

The disk-column append only hit GetNodeByID (whitespace differed); ListNodes
lacked last_disk_pct/disk_total_gb, so the node list 500'd and rendered empty.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/render/internal/db/db.go

@@ -31,7 +31,8 @@ func (s *Store) ListNodes(ctx context.Context, region, status string) ([]*models
 	             lifetime_task_count, lifetime_crash_count, consecutive_failures,
 	             priority, is_active, accepts_new_jobs,
 	             last_maintenance_at, next_maintenance_at, maintenance_reason,
-	             cached_template_md5s, cache_used_gb, created_at, updated_at
+	             cached_template_md5s, cache_used_gb, created_at, updated_at,
+	             last_disk_pct, disk_total_gb
 	      FROM render.render_nodes
 	      WHERE is_active = TRUE`
 	args := pgx.NamedArgs{}