docs: consolidate upgrade guides into single v0.4.0 migration doc

Split changelog content from migration guide per review feedback.
Move new features and bug fixes to CHANGELOG.md, slim the upgrade
guide to config-only migration steps. Remove v0.3.0 upgrade guide
as v0.4.0 now covers upgrades from all previous versions.

Author: randygrok

CHANGELOG.md

@@ -9,18 +9,26 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- `EV_TRACE_LEVEL` env var to control OTLP span export verbosity independently from `RUST_LOG` stdout log level ([#156](https://github.com/evstack/ev-reth/issues/156))
+- `ev-deployer` CLI (`bin/ev-deployer`) for generating genesis alloc entries with embedded contract bytecodes ([#167](https://github.com/evstack/ev-reth/pull/167))
 - `ev-dev` binary (`bin/ev-dev`): one-command local development chain with pre-funded Hardhat accounts, similar to Anvil or Hardhat Node
 - Transaction sponsor service (`bin/sponsor-service`) for signing EvNode transactions on behalf of users via JSON-RPC proxy ([#141](https://github.com/evstack/ev-reth/pull/141))
+- Granular tracing instrumentation spans across payload building, transaction validation, and EVM execution
+- `EV_TRACE_LEVEL` env var to control OTLP span export verbosity independently from `RUST_LOG` stdout log level ([#156](https://github.com/evstack/ev-reth/issues/156))
 
 ### Changed
 
+- Upgraded Reth from v1.11.x to v2.0.0 with Storage V2 support, revm 36.0.0, and alloy-evm 0.30.0 ([#207](https://github.com/evstack/ev-reth/pull/207))
+- `reth-primitives` imports migrated to `alloy_consensus` and `reth_ethereum_primitives` (upstream crate removed)
+- Txpool fallback (pulling pending transactions when Engine API attributes are empty) restricted to `--dev` mode only
+- Migrated build system from Makefile to Justfile
 - Removed unused `thiserror` dependency from `ev-precompiles` crate
 
 ### Fixed
 
+- Payload builder now uses `decode_2718_exact` instead of `network_decode` for Engine API payloads, fixing silent drops of valid type 0x76 and EIP-1559/EIP-2930 transactions ([#219](https://github.com/evstack/ev-reth/pull/219))
 - Payload builder now pulls pending transactions from the txpool in `--dev` mode, fixing `cast send` and other RPC-submitted transactions not being included in blocks
 - Txpool now uses sponsor balance for pending/queued ordering in sponsored EvNode transactions, and validates executor balance separately for call value transfers ([#141](https://github.com/evstack/ev-reth/pull/141))
+- Additional test coverage for deploy allowlist edge cases across all transaction types
 
 ## [0.3.0] - 2026-02-23