Integrate Atlas as alternative to Blockscout in eth-explorer stack

[tac0turtle]

Once Atlas is production-ready, we should evaluate replacing or offering it alongside Blockscout in the ev-stacks/stacks/eth-explorer stack.

Why:

• Atlas is purpose-built for ev-node chains — lighter footprint, faster indexing (binary COPY, cursor pagination), and simpler deployment (3 containers vs Blockscout's larger stack).
• Repo: https://github.com/evstack/atlas

Action items:

• Validate Atlas stability and feature coverage against current Blockscout usage
• Add Atlas as a stack option in ev-stacks/stacks/eth-explorer
• Decide whether to keep Blockscout as a fallback or fully replace

Not urgent — blocked on Atlas reaching confidence for production use.