add block height modified to legacy data

[cody-littley]

Describe your changes and provide context

Add the block height modified metadata to the legacy store

Testing performed to validate your change

updated unit tests

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Apr 20, 2026, 8:06 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.31%. Comparing base (a3bb4e8) to head (03e1761).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3276   +/-   ##
=======================================
  Coverage   59.31%   59.31%           
=======================================
  Files        2071     2072    +1     
  Lines      169866   169916   +50     
=======================================
+ Hits       100755   100793   +38     
- Misses      60335    60345   +10     
- Partials     8776     8778    +2     

Flag	Coverage Δ
sei-chain-pr	77.72% <100.00%> (?)
sei-db	70.41% <ø> (ø)

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Files with missing lines	Coverage Δ
sei-db/state_db/sc/flatkv/store_apply.go	90.22% <100.00%> (+1.72%)	⬆️
sei-db/state_db/sc/flatkv/vtype/legacy_data.go	100.00% <100.00%> (+6.38%)	⬆️

... and 2 files with indirect coverage changes

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