feat(provision): 弹性节点基建 Terraform + 一键更换 (tsk_6u0FxmbC7Yeq)

IaC 面 (infra/) 与控制面 (server/internal/provision) 双产出，落地 doc/04 §4
「节点是牲口」弹性拓扑与 make-before-break 一键更换。

server/internal/provision:
- CloudAdapter 适配层 + Registry（首发 vultr 消耗品池 / hetzner 精品池各一）；
  厂商凭证仅从 PROVISION_<VENDOR>_* env 注入，不入库不入 git。
- ProvisionService：CreateNode(幂等键重放不重复开机)、DestroyNode(幂等)、
  RotateIP(换 IP 不换机 + version bump)、ListProviders。
- Replace 一键更换：先建后拆，新机 up 先于旧机 draining（容量不下降），
  replacement_uuid 幂等键 + replacements 表分步记录，崩溃可续跑不重复。
- RotatePool：池内滚动轮换，并发度 1–2。
- cmd/nodectl CLI：create/destroy/rotate-ip/replace/rotate-pool/providers。
- 单测（mock 厂商 API + 内存 Store）：幂等重放、make-before-break 时序断言、
  开机失败/探活超时→destroyed+失败计数+告警钩子、崩溃续跑、RotatePool。

infra/:
- terraform/：探针机 + 控制面基线模块化（probe / control-plane）+ README，
  低频基线进 state，节点不进 Terraform。
- cloud-init/node.yaml.tmpl：节点引导模板（注入一次性 bootstrap token，task #5）。
- identity-isolation.md：身份隔离登记表（doc/06 §2 红线，无任何凭证）。

migrations/000008：nodes 增 provider_instance_id/elastic_ip_id、node_events
增 ip_rotated、provision_idempotency / replacements 表（附加式，不动现网）。

红线：仅面向新厂商池，绝不纳管现网生产 EC2(deploy/ marzban)。

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

server/internal/provision/store.go

@@ -0,0 +1,81 @@
+package provision
+
+import (
+	"context"
+	"time"
+)
+
+// ReplaceStep enumerates the resumable steps of a Replace orchestration.
+// Persisted in replacements.step so a crashed process can continue without
+// repeating a boot or a destroy.
+type ReplaceStep string
+
+const (
+	StepOpenNew    ReplaceStep = "open_new"    // create the replacement node
+	StepProbing    ReplaceStep = "probing"     // wait for self-register + probe
+	StepNewUp      ReplaceStep = "new_up"      // promote new node, bump version
+	StepDraining   ReplaceStep = "draining"    // drain the old node
+	StepDestroyOld ReplaceStep = "destroy_old" // destroy old node + release IP
+	StepDone       ReplaceStep = "done"
+)
+
+// ReplaceStatus is the terminal/running state of a replacement record.
+type ReplaceStatus string
+
+const (
+	ReplaceRunning ReplaceStatus = "running"
+	ReplaceDone    ReplaceStatus = "done"
+	ReplaceFailed  ReplaceStatus = "failed"
+)
+
+// Replacement mirrors a replacements row (crash-recoverable orchestration).
+type Replacement struct {
+	UUID      string
+	OldNodeID int64
+	NewNodeID int64 // 0 until the new node is created
+	Pool      Pool
+	Status    ReplaceStatus
+	Step      ReplaceStep
+	CreatedAt time.Time
+	UpdatedAt time.Time
+}
+
+// Store is the persistence boundary for the provision package. Both the MySQL
+// implementation (mysqlStore) and the in-memory test fake satisfy it, keeping
+// the service / orchestration logic database-agnostic and unit-testable.
+type Store interface {
+	// --- nodes ---
+	InsertNode(ctx context.Context, n *Node) (int64, error)
+	GetNode(ctx context.Context, id int64) (*Node, error)
+	GetNodeByUUID(ctx context.Context, uuid string) (*Node, error)
+	UpdateNodeStatus(ctx context.Context, id int64, status Status) error
+	UpdateNodeEndpoint(ctx context.Context, id int64, endpoint string) error
+	// SetNodeInstance records the vendor instance ID and IP-derived endpoint.
+	SetNodeInstance(ctx context.Context, id int64, instanceID, endpoint string) error
+	SetNodeWeight(ctx context.Context, id int64, weight int) error
+	// ListNodesByPool returns nodes whose provider belongs to pool, optionally
+	// filtered to a single status (empty = all statuses).
+	ListNodesByPool(ctx context.Context, pool Pool, status Status) ([]*Node, error)
+
+	// --- providers ---
+	ListProviders(ctx context.Context, pool Pool) ([]*Provider, error)
+	GetProvider(ctx context.Context, id int64) (*Provider, error)
+
+	// --- events / audit / directory ---
+	WriteNodeEvent(ctx context.Context, nodeID int64, event Event, detailJSON string) error
+	WriteAuditLog(ctx context.Context, actor, action, target, metaJSON string) error
+	BumpDirectoryVersion(ctx context.Context) (int64, error)
+
+	// --- idempotency ---
+	// LookupIdempotency returns the node UUID previously bound to key, or
+	// (\"\", false, nil) if unseen.
+	LookupIdempotency(ctx context.Context, key string) (string, bool, error)
+	// SaveIdempotency binds key→nodeUUID. It is a no-op if the key already
+	// exists (first write wins).
+	SaveIdempotency(ctx context.Context, key, nodeUUID string) error
+
+	// --- replacements (crash recovery) ---
+	CreateReplacement(ctx context.Context, r *Replacement) error
+	GetReplacement(ctx context.Context, uuid string) (*Replacement, error)
+	UpdateReplacement(ctx context.Context, r *Replacement) error
+}