feat(server/db): 多库(3/4)— Dialect 抽象(upsert/锁)+ 合并 directory_version

- db.Dialect:LockForUpdate(mysql "FOR UPDATE" / sqlite "")、Upsert(中性
  EXCLUDED.col → mysql VALUES()/ sqlite excluded.);DialectForDB 从连接驱动推导
- 9 处 ON DUPLICATE KEY、11 处 FOR UPDATE 全走 dialect;sqlite 靠 _txlock=
  immediate 取得 BEGIN IMMEDIATE 悲观锁等价语义
- directory_version 三处重复合并为 store.BumpDirectoryVersion(dialect 感知)
- 这些文件同时含(2/4)的 UTC→Go 改动(与 upsert/锁同语句交错,无法拆分)
- 顺带:usage 的 FIELD()、codes 的 DATE_ADD/GREATEST 续期、nodes 的
  UNIX_TIMESTAMP、NULLIF 等 MySQL 专属构造一并退回 Go/可移植写法

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

server/internal/nodes/lifecycle.go

@@ -6,10 +6,13 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"time"
 
 	"github.com/redis/go-redis/v9"
 
+	dbx "github.com/wangjia/pangolin/server/internal/db"
 	"github.com/wangjia/pangolin/server/internal/mtls"
+	"github.com/wangjia/pangolin/server/internal/store"
 )
 
 // ErrInvalidTransition is returned when the requested status transition is not
@@ -56,9 +59,10 @@ type transitionSpec struct {
 //
 // Called by #15 (block-detection / drain scheduler) and #14 (provisioning).
 type Lifecycle struct {
-	db  *sql.DB
-	crl *mtls.CRL    // for MarkDestroyed post-commit hook
-	rdb redis.Cmdable // for MarkDestroyed post-commit cleanup
+	db      *sql.DB
+	dialect dbx.Dialect
+	crl     *mtls.CRL     // for MarkDestroyed post-commit hook
+	rdb     redis.Cmdable // for MarkDestroyed post-commit cleanup
 }
 
 // NewLifecycle constructs a Lifecycle.
@@ -66,22 +70,13 @@ type Lifecycle struct {
 //   - crl: mTLS revocation manager (task 5b, mtls.NewCRL)
 //   - rdb: Redis client or Cmdable (for post-destroy key cleanup)
 func NewLifecycle(db *sql.DB, crl *mtls.CRL, rdb redis.Cmdable) *Lifecycle {
-	return &Lifecycle{db: db, crl: crl, rdb: rdb}
+	return &Lifecycle{db: db, dialect: dbx.DialectForDB(db), crl: crl, rdb: rdb}
 }
 
 // BumpVersion atomically increments the directory_version singleton within tx.
-//
-// Signature matches the one defined by task 5d (BumpVersion(ctx, tx)); if 5d
-// has merged, remove this copy and update callers to use the 5d version.
-func BumpVersion(ctx context.Context, tx *sql.Tx) error {
-	_, err := tx.ExecContext(ctx,
-		`INSERT INTO directory_version (id, version) VALUES (1, 1)
-		 ON DUPLICATE KEY UPDATE version = version + 1`,
-	)
-	if err != nil {
-		return fmt.Errorf("nodes.BumpVersion: %w", err)
-	}
-	return nil
+// Delegates to the canonical store.BumpDirectoryVersion (dialect-aware).
+func BumpVersion(ctx context.Context, tx *sql.Tx, d dbx.Dialect) error {
+	return store.BumpDirectoryVersion(ctx, tx, d)
 }
 
 // MarkProbing transitions a node from provisioning → probing.
@@ -197,14 +192,14 @@ func (l *Lifecycle) MarkBlockedSuspect(ctx context.Context, nodeUUID string, det
 		return fmt.Errorf("lifecycle.MarkBlockedSuspect: marshal detail: %w", err)
 	}
 	if _, err := tx.ExecContext(ctx,
-		`INSERT INTO node_events (node_id, event, detail, at) VALUES (?, ?, ?, UTC_TIMESTAMP(6))`,
-		nodeID, string(eventBlockedSuspect), detailJSON,
+		`INSERT INTO node_events (node_id, event, detail, at) VALUES (?, ?, ?, ?)`,
+		nodeID, string(eventBlockedSuspect), detailJSON, time.Now().UTC(),
 	); err != nil {
 		return fmt.Errorf("lifecycle.MarkBlockedSuspect: insert event: %w", err)
 	}
 
 	// Bump directory version.
-	if err := BumpVersion(ctx, tx); err != nil {
+	if err := BumpVersion(ctx, tx, l.dialect); err != nil {
 		return err
 	}
 
@@ -265,15 +260,15 @@ func (l *Lifecycle) transact(
 
 		// Insert the event record.
 		if _, err := tx.ExecContext(ctx,
-			`INSERT INTO node_events (node_id, event, detail, at) VALUES (?, ?, ?, UTC_TIMESTAMP(6))`,
-			nodeID, string(spec.event), detailJSON,
+			`INSERT INTO node_events (node_id, event, detail, at) VALUES (?, ?, ?, ?)`,
+			nodeID, string(spec.event), detailJSON, time.Now().UTC(),
 		); err != nil {
 			return fmt.Errorf("lifecycle.transact: insert event [%s→%s]: %w",
 				spec.from, spec.to, err)
 		}
 
 		// Bump the global directory version.
-		if err := BumpVersion(ctx, tx); err != nil {
+		if err := BumpVersion(ctx, tx, l.dialect); err != nil {
 			return err
 		}