feat(nodes): 节点生命周期状态机 [tsk_aG4yOS90inF_]

实现 Lifecycle 类型及其全部公开方法，覆盖 6 个状态迁移动作：
MarkProbing / MarkUp / MarkDraining / MarkDown / MarkDestroyed /
MarkBlockedSuspect。每次合法迁移在同一个 SQL 事务中原子执行
UPDATE nodes + INSERT node_events + BumpVersion；MarkDestroyed
事务提交后异步调用 mtls.CRL.Revoke() 并清除 Redis 负载缓存与
命令队列键。配套集成测试覆盖 5 类场景（合法迁移、非法迁移、
并发写、后置钩子、blocked_suspect 幂等），全部通过。

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

server/run_mysql_test.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+# Start a MySQL 8 container, wait for it to be ready, run lifecycle integration tests, and clean up.
+set -e
+
+CONTAINER_NAME="lc-mysql-$(date +%s)"
+PORT=13307
+
+echo "Starting MySQL container: $CONTAINER_NAME on port $PORT"
+docker run -d \
+  --name "$CONTAINER_NAME" \
+  -e MYSQL_ROOT_PASSWORD=secret \
+  -e MYSQL_DATABASE=pangolin_test \
+  -p "$PORT:3306" \
+  mysql:8 >/dev/null
+
+cleanup() {
+  echo "Stopping container $CONTAINER_NAME"
+  docker stop "$CONTAINER_NAME" >/dev/null 2>&1 || true
+  docker rm   "$CONTAINER_NAME" >/dev/null 2>&1 || true
+}
+trap cleanup EXIT
+
+# Wait for MySQL to be ready (max 60 s)
+echo "Waiting for MySQL to be ready..."
+for i in $(seq 1 30); do
+  if docker exec "$CONTAINER_NAME" mysqladmin ping --silent 2>/dev/null; then
+    echo "MySQL ready after ${i}*2 seconds"
+    break
+  fi
+  sleep 2
+done
+
+DSN="root:secret@tcp(127.0.0.1:${PORT})/pangolin_test"
+echo "Running lifecycle integration tests with DSN=$DSN"
+
+PANGOLIN_TEST_DSN="$DSN" go test -tags integration \
+  ./internal/nodes/... \
+  -run "TestLifecycle" \
+  -v -count=1 -timeout 120s
+
+echo "Tests complete"