Update go.mod module line, all require/replace directives, and every
.go import path from forge.lthn.ai/core/go-blockchain to
dappco.re/go/core/blockchain. Add replace directives to bridge
dappco.re paths to existing forge.lthn.ai registry during migration.
Update CLAUDE.md, README, and docs to reflect the new module path.
Co-Authored-By: Virgil <virgil@lethean.io>
Block major version validation covering all hardfork transitions.
Single expectedBlockMajorVersion function handles HF0→HF4.
Co-Authored-By: Charon <charon@lethean.io>
