refactor: remove go-fraud dependency and related dead code

[rootulp]

Summary

Closes #4930

Remove the github.com/celestiaorg/go-fraud dependency from celestia-node. Fraud proofs are no longer functional post-shwap and there are no plans to reintroduce them. This reduces maintenance burden and allows archiving the go-fraud repository.

What was removed

• nodebuilder/fraud/ — entire package (Module interface, API, ServiceBreaker, constructors, proof unmarshaler, mocks)
• share/eds/byzantine/bad_encoding.go — BadEncodingProof (BEFP) implementation and tests
• share/eds/byzantine/pb/ — protobuf definitions for BEFP serialization
• header/headertest/fraud/ — FraudMaker test helper
• nodebuilder/tests/fraud_test.go — fraud integration test (was already skipped)
• Fraud pubsub topics — removed from gossipsub scoring
• Fraud RPC endpoint — removed from server registration and client
• github.com/celestiaorg/go-fraud — removed from go.mod

What was preserved

• share/eds/byzantine/byzantine.go — ErrByzantine type (still used by cascade getter and full availability for error classification)
• share/eds/byzantine/share_proof.go — ShareWithProof type and GetShareWithProof (still used by ErrByzantine)

Test plan

• go build ./... passes
• go test ./das/ passes
• go test ./share/eds/ passes (including renamed TestByzantineError)
• go test ./api/... passes (including TestModulesImplementFullAPI)
• No remaining references to go-fraud, nodebuilder/fraud, BadEncodingProof, or ServiceBreaker

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 35.90%. Comparing base (2469e7a) to head (89198d2).
⚠️ Report is 747 commits behind head on main.

Files with missing lines	Patch %	Lines
nodebuilder/das/constructors.go	0.00%	1 Missing ⚠️
nodebuilder/p2p/pubsub.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4933      +/-   ##
==========================================
- Coverage   44.83%   35.90%   -8.93%     
==========================================
  Files         265      305      +40     
  Lines       14620    20887    +6267     
==========================================
+ Hits         6555     7500     +945     
- Misses       7313    12395    +5082     
- Partials      752      992     +240     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[rootulp]

Recreating from upstream branch to fix CI permissions.