Update GetNodes endpoint

[fbac]

Update the Service.GetNodes endpoint to return a map of node IDs to HTTP addresses for the GetNodes endpoint

This change updates the Service.GetNodes handler to return a map keyed by node ID to HTTP address and regenerates associated protocol and OpenAPI definitions to reflect the new response shape.

• Modify Service.GetNodes to build and return map[uint32]string keyed by node.NodeID instead of a []string of HTTP addresses in service.go
• Update generated Protobuf to switch GetNodesResponse.Nodes from []string to map[uint32]string with NodesEntry in payer_api.pb.go
• Update OpenAPI schema to represent GetNodesResponse.nodes as an object with additionalProperties in payer_api.swagger.json

📍Where to Start

Start with the Service.GetNodes handler in service.go.

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Macroscope summarized f176dd9.

[graphite-app]

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