Replace NodeID field access with ID() method across the codebase

[coderabbitai]

As requested by @wdbaruni, opening this issue to address the TODO comment about replacing direct access to the NodeID field with the ID() method throughout the codebase.

PR: #4687
Comment: #4687 (comment)

Key locations needing updates:

• pkg/node/node.go: Multiple direct NodeID accesses in node configuration
• pkg/orchestrator/watchers/: Multiple dispatcher implementations accessing NodeID directly
• pkg/node/manager/: Direct NodeID access in node management logic
• pkg/node/heartbeat/: Several direct accesses in heartbeat handling

[linear]

ENG-307 Replace NodeID field access with ID() method across the codebase