ops: rebalance container memory limits (node-exporter 32m, cadvisor 192m)

node-exporter only uses ~20MB so 32m is safe. cadvisor was at 98% of
128m and crashing during CI runs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -210,7 +210,7 @@ services:
       - "--path.sysfs=/host/sys"
       - "--path.rootfs=/rootfs"
       - "--collector.filesystem.mount-points-exclude=^/(sys|proc|dev|host|etc)($$|/)"
-    mem_limit: 64m
+    mem_limit: 32m
     healthcheck:
       test: ["CMD-SHELL", "wget -qO- http://localhost:9100/metrics | grep -q 'node_exporter_build_info' || exit 1"]
       interval: 30s
@@ -235,7 +235,7 @@ services:
     privileged: true
     devices:
       - /dev/kmsg
-    mem_limit: 128m
+    mem_limit: 192m
     networks:
       - monitoring