[BUG] Handle node deletion, label selector unmatching, and status drift in NodeReconciler

What happened?

When a node is deleted from the cluster, NodeReconciler.Reconcile gets a NotFound error from r.Get and silently swallows it via client.IgnoreNotFound(err). The deleted node is never removed from rule.Status.NodeEvaluations, AppliedNodes, or FailedNodes on any rule, and the node_readiness_nodes_by_state metric keeps counting it forever.

Separately, RuleReconciler.cleanupDeletedNodes only filters NodeEvaluations — it misses AppliedNodes and FailedNodes, so those two fields also go stale.

Two related points originally filed here are split out per this review:

• AppliedNodes real-time sync — deferred until #89 lands (per-node status is moving out of rule.status entirely).
• Orphaned taints on selector unmatch — moved to #342 (needs its own design discussion).

Expected behavior

• Deleting a node removes it from NodeEvaluations, AppliedNodes, and FailedNodes on every rule, and updates the metric.
• cleanupDeletedNodes cleans up all three fields, not just NodeEvaluations.

Repro

1. Create a NodeReadinessRule matching worker nodes.
2. Confirm a node shows up in rule.Status.NodeEvaluations/AppliedNodes.
3. kubectl delete node worker-1.
4. worker-1 is still in the rule status and in /metrics.

Affected components

• internal/controller/node_controller.go (Reconcile)
• internal/controller/nodereadinessrule_controller.go (cleanupDeletedNodes)

Controller version / K8s version

main (v0.4.1+) / v1.30.0–v1.31.0