feat(volume): cli on-demand snapshot checksum for volume

[davidcheng0922]

Which issue(s) this PR fixes:

longhorn/longhorn#11442

What this PR does / why we need it:

• Support for on-demand snapshot checksum calculation.
• Update vendor dependency

Special notes for your reviewer:

Usage sample:

./longhornctl-linux-amd64 checksum volume --name=v1 --namespace=longhorn-system

Sample output:

[ec2-user@ip-172-31-2-165 cli]$ ./longhornctl-linux-amd64 checksum volume --name=v1 --namespace=longhorn-system
I0130 06:48:20.027543  257530 shared_informer.go:349] "Waiting for caches to sync" controller="longhorn datastore"
I0130 06:48:20.101704  257530 warnings.go:107] "Warning: v1 Endpoints is deprecated in v1.33+; use discovery.k8s.io/v1 EndpointSlice"
I0130 06:48:20.147017  257530 shared_informer.go:356] "Caches are synced" controller="longhorn datastore"
INFO[2026-01-30T06:48:20Z] Triggering on-demand snapshot checksum calculation  volume=v1
INFO[2026-01-30T06:48:20Z] Snapshot snap-a43073525b7a48f7 has no checksum; scheduling calculation 
INFO[2026-01-30T06:48:20Z] Snapshot snap-54e6c825285644c8 has no checksum; scheduling calculation 
INFO[2026-01-30T06:48:20Z] Requested on-demand checksum calculation for volume v1 
INFO[2026-01-30T06:48:20Z] Calculating snapshot checksums may take some time.You can check progress in the Longhorn UI or with kubectl. 
INFO[2026-01-30T06:48:20Z] Checksum request submitted                    volume=v1
INFO[2026-01-30T06:48:20Z] Cleaning volume on-demand checksum requester  volume=v1
INFO[2026-01-30T06:48:20Z] Completed volume on-demand checksum requester  volume=v1

And user check the snapshot checksum themselves.

Additional documentation or context

[codecov]

Codecov Report

❌ Patch coverage is 0% with 93 lines in your changes missing coverage. Please review.
✅ Project coverage is 2.63%. Comparing base (03943a5) to head (1a5b97b).

Files with missing lines	Patch %	Lines
pkg/remote/volume/hasher.go	0.00%	44 Missing ⚠️
cmd/remote/subcmd/checksum.go	0.00%	42 Missing ⚠️
pkg/utils/kubernetes/client.go	0.00%	6 Missing ⚠️
cmd/remote/longhornctl.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #392      +/-   ##
=========================================
- Coverage    2.70%   2.63%   -0.08%     
=========================================
  Files          39      41       +2     
  Lines        3471    3564      +93     
=========================================
  Hits           94      94              
- Misses       3375    3468      +93     
  Partials        2       2              

Flag	Coverage Δ
unittests	2.63% <0.00%> (-0.08%)	⬇️

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