Cjl/litt db compiling

[cody-littley]

Describe your changes and provide context

Enables us to build LittDB. The initial batch of files could not compile in their unmodified form.

• Copied over a few utility functions that lived outside of the litt package (i.e. it was in the EigenDA common package, or equivalent)
• fixed package paths to point to the new sei path, not the old eigenDA paths
• renamed the cache package since the sei repo .gitignore ignores any directlry named "cache"
• created a go.mod / go.sum for the litt package, this is temporary and will be deleted in a follow up PR

Still detached from regular build system (i.e. doesn't build in CI pipeline) since I want to remove some external dependencies before we fully integrate. Can be built by running the following:

cd sei-db/db_engine/litt 
make build-all

[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 23, 2026, 8:02 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.28%. Comparing base (c3622b1) to head (3a696c4).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3307      +/-   ##
==========================================
- Coverage   59.14%   58.28%   -0.87%     
==========================================
  Files        2085     2085              
  Lines      170876   208744   +37868     
==========================================
+ Hits       101069   121668   +20599     
- Misses      61017    78287   +17270     
+ Partials     8790     8789       -1     

Flag	Coverage Δ
sei-db	70.41% <ø> (ø)

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see 1803 files with indirect coverage changes

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