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/scheduler/wiring_lifecycle.go

@@ -8,9 +8,11 @@ import (
 	"strings"
 	"time"
 
+	dbx "github.com/wangjia/pangolin/server/internal/db"
 	"github.com/wangjia/pangolin/server/internal/nodes"
 	"github.com/wangjia/pangolin/server/internal/scheduler/detect"
 	"github.com/wangjia/pangolin/server/internal/scheduler/orchestrate"
+	"github.com/wangjia/pangolin/server/internal/store"
 )
 
 // SQLLifecycle is a MySQL-backed lifecycle store. The detect and orchestrate
@@ -30,13 +32,14 @@ import (
 // — provision.DestroyNode tears down the VM, and the agent's mTLS cert can be
 // revoked separately. Wire CRL revocation when the real fleet exists (TODO).
 type SQLLifecycle struct {
-	db    *sql.DB
-	loads *nodes.LoadCache
+	db      *sql.DB
+	dialect dbx.Dialect
+	loads   *nodes.LoadCache
 }
 
 // NewSQLLifecycle wires the store. loads may be nil (load reads then return zero).
 func NewSQLLifecycle(db *sql.DB, loads *nodes.LoadCache) *SQLLifecycle {
-	return &SQLLifecycle{db: db, loads: loads}
+	return &SQLLifecycle{db: db, dialect: dbx.DialectForDB(db), loads: loads}
 }
 
 const nodeSelectCols = `id, uuid, status, region, tier, role, reality_sni, reality_pbk, hy2_port, provider_id, weight, name_zh, name_en`
@@ -134,9 +137,7 @@ func (l *SQLLifecycle) transition(ctx context.Context, nodeID, from, to string,
 		_, _ = tx.ExecContext(ctx,
 			`INSERT INTO node_events (node_id, event, detail) VALUES (?, ?, ?)`, nodeID, ev, dj)
 	}
-	if _, err := tx.ExecContext(ctx,
-		`INSERT INTO directory_version (id, version) VALUES (1, 1)
-		 ON DUPLICATE KEY UPDATE version = version + 1`); err != nil {
+	if err := store.BumpDirectoryVersion(ctx, tx, l.dialect); err != nil {
 		return 0, err
 	}
 	if err := tx.Commit(); err != nil {
@@ -151,10 +152,7 @@ func (l *SQLLifecycle) setWeight(ctx context.Context, nodeID string, weight int)
 }
 
 func (l *SQLLifecycle) bumpVersion(ctx context.Context) error {
-	_, err := l.db.ExecContext(ctx,
-		`INSERT INTO directory_version (id, version) VALUES (1, 1)
-		 ON DUPLICATE KEY UPDATE version = version + 1`)
-	return err
+	return store.BumpDirectoryVersion(ctx, l.db, l.dialect)
 }
 
 func (l *SQLLifecycle) version(ctx context.Context) int64 {