Backport release/v6.6: Update v6.6 change log in prep to cut v6.6.3 patch

[seidroid]

Backport of #4033 to release/v6.6.

[seidroid]

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin backport-4033-to-release/v6.6
git worktree add --checkout .worktree/backport-4033-to-release/v6.6 backport-4033-to-release/v6.6
cd .worktree/backport-4033-to-release/v6.6
git reset --hard HEAD^
git cherry-pick -x ea3836f1a987a3fd31820fcb6c0078e625bf50e7
git push --force-with-lease

[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	Aug 28, 2026, 6:07 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.20%. Comparing base (d2e7ad2) to head (75c1e0f).
⚠️ Report is 1 commits behind head on release/v6.6.

Additional details and impacted files

@@               Coverage Diff                @@
##           release/v6.6    #4055      +/-   ##
================================================
- Coverage         59.11%   58.20%   -0.91%     
================================================
  Files              2231     2157      -74     
  Lines            184599   175837    -8762     
================================================
- Hits             109119   102354    -6765     
+ Misses            65646    64357    -1289     
+ Partials           9834     9126     -708     

Flag	Coverage Δ
sei-db	69.80% <ø> (ø)
sei-db-state-db	?

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[cursor]

PR Summary

Low Risk
Documentation-only changelog update with no runtime or API changes.

Overview
Updates the v6.6 section of CHANGELOG.md so release notes match backports landed on release/v6.6 ahead of cutting v6.6.3 (backport of #4033).

The section gains nine new bullet entries at the top (PRs #4053 through #3965), covering snapshot validation, memiavl snapshot fixes, frozen RPC router hardening, historical EVM freeze mode, and v6.6.2 version/changelog prep. The existing #4006 line is reworded to “Disable mempool traffic in freeze mode” instead of the longer transaction/evidence/gossip wording.

^{Reviewed by Cursor Bugbot for commit 75c1e0f. Bugbot is set up for automated code reviews on this repo. Configure here.}