br restore failed with panic when pd rolling restart

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)
1，run br restore
2，pd rolling restart

### 2. What did you expect to see? (Required)
br restore can succeed

### 3. What did you see instead (Required)
br restore failed with panic
2026/04/19 12:31:54.360 +00:00] [PANIC] [safepoint.go:110] ["cannot pass gc safe point check, aborting"] [error="GC safepoint 465725239969185792 exceed TS 465725230251507715: [BR:Backup:ErrBackupGCSafepointExceeded]backup GC safepoint exceeded"] [errorVerbose="[BR:Backup:ErrBackupGCSafepointExceeded]backup GC safepoint exceeded\nGC safepoint 465725239969185792 exceed TS 465725230251507715\ngithub.com/pingcap/tidb/br/pkg/gc.CheckGCSafePoint\n\t/workspace/source/tidb/br/pkg/gc/safepoint.go:65\ngithub.com/pingcap/tidb/br/pkg/gc.StartServiceSafePointKeeper.func1\n\t/workspace/source/tidb/br/pkg/gc/safepoint.go:109\nruntime.goexit\n\t/usr/local/go/src/runtime/asm_amd64.s:1693"] [safePoint="{ID=br-0deae0db-ce2b-46e4-83a9-780a6b2aa844,TTL=5m0s,BackupTime=\"2026-04-19 12:12:42.373 +0000 UTC\",BackupTS=465725230251507715}"] [stack="github.com/pingcap/tidb/br/pkg/gc.StartServiceSafePointKeeper.func1\n\t/workspace/source/tidb/br/pkg/gc/safepoint.go:110"]

[br.log.2026-04-19T12.12.41Z.zip](https://github.com/user-attachments/files/26972254/br.log.2026-04-19T12.12.41Z.zip)

### 4. What is your TiDB version? (Required)
./br -V
Release Version: v9.0.0-beta.2.pre-1584-ga10a43ada5
Git Commit Hash: a10a43ada5abe6cbd7ce5e4a9f3ca7654089ee34
Git Branch: HEAD
Go Version: go1.25.8
UTC Build Time: 2026-04-19 05:06:43
Race Enabled: false
Kernel Type: Classic