fix(frontend): restore DEX pools feature

[JOY (JOY)]

Summary

• restore NEXT_PUBLIC_DEX_POOLS_ENABLED in the shared frontend environment
• keep mainnet and testnet feature parity

Production evidence

• /pools currently returns the frontend 404 because the flag is absent
• the contract-info pools endpoint for chain 7979 is healthy and currently returns an empty items list

Validation

• git diff --check

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.