fix: staking optimization

[randy-cro]

Description

This patch introduces a fixed gas consumption decorator in the antehandler to standardize gas usage for whitelisted messages.
Currently, only staking-related messages are included in the whitelist.

Purpose

This ensures consistent gas consumption across all nodes, regardless of variations in staking cache size.
By normalizing gas usage, it prevents potential AppHash mismatches caused by node-specific performance differences.

Implementation Details

• A fixed gas amount is assigned per whitelisted message type.
• The values are derived from the average gas usage observed on mainnet.

For example, the mean gas used for MsgUndelegate can be referenced here:
Mainnet reference

This change works in tandem with the staking cache introduced in the Cosmos SDK:
crypto-org-chain/cosmos-sdk#1733

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For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

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For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
• Reviewers assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	golang/​github.com/​randy-cro/​cosmos-sdk@​v0.0.0-20251113072857-fbecd698368d

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 46.97%. Comparing base (d8a1c9e) to head (200a3fa).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #776      +/-   ##
===========================================
+ Coverage    46.85%   46.97%   +0.12%     
===========================================
  Files          189      190       +1     
  Lines        15353    15389      +36     
===========================================
+ Hits          7193     7229      +36     
  Misses        7361     7361              
  Partials       799      799              

Files with missing lines	Coverage Δ
ante/cosmos/fixed_gas.go	100.00% <100.00%> (ø)
evmd/ante/evm_handler.go	100.00% <100.00%> (ø)
evmd/ante/handler_options.go	61.05% <100.00%> (+0.41%)	⬆️
evmd/app.go	78.76% <100.00%> (+0.22%)	⬆️

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