Upgrade Heimdall Nodes Before June 25 Hard Fork

Heimdall v0.9.0 released for Polygon mainnet. Zurich HF set for block 47,880,000 on June 25th, ~2PM UTC. All node operators must upgrade immediately. Requires config changes and specific Bor versions. Upgrade steps: stop heimdalld, install v0.9.0 with network and node type, verify version, restart service.