fix flatkv snapshot import export metadata

[Kbhat1]

Summary

Test plan

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Apr 9, 2026, 5:16 PM

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 58.51%. Comparing base (289bc61) to head (9960ddd).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-db/state_db/sc/flatkv/store_read.go	0.00%	1 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) is below the target coverage (50.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3217      +/-   ##
==========================================
- Coverage   59.02%   58.51%   -0.51%     
==========================================
  Files        2065     2099      +34     
  Lines      169349   172677    +3328     
==========================================
+ Hits        99960   101047    +1087     
- Misses      60630    62529    +1899     
- Partials     8759     9101     +342     

Flag	Coverage Δ
sei-db	70.41% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
sei-db/common/evm/keys.go	91.48% <ø> (ø)
sei-db/state_db/sc/composite/exporter.go	80.48% <ø> (-0.47%)	⬇️
sei-db/state_db/sc/composite/importer.go	92.00% <ø> (-0.60%)	⬇️
sei-db/state_db/sc/flatkv/exporter.go	71.18% <ø> (-12.91%)	⬇️
sei-db/state_db/sc/flatkv/importer.go	34.37% <ø> (-37.72%)	⬇️
sei-db/state_db/sc/flatkv/iterator.go	37.03% <ø> (-42.38%)	⬇️
sei-db/state_db/sc/flatkv/keys.go	100.00% <ø> (ø)
sei-db/state_db/sc/flatkv/store.go	70.51% <ø> (-2.76%)	⬇️
sei-db/state_db/sc/flatkv/store_write.go	75.60% <ø> (-10.00%)	⬇️
sei-db/state_db/ss/composite/store.go	67.77% <ø> (-2.66%)	⬇️
... and 1 more

... and 221 files with indirect coverage changes

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