feat: make addresses indexes for orders optional

[pablocampogo]

Summary

• Added IndexOrdersByAddresses configuration option to StateMachineConfig that controls whether secondary indexes for order lookups by seller/buyer address are created
• When disabled, the /v1/query/orders endpoint returns an error if sellersSendAddress or buyerSendAddress filters are used
• Default value is true (indexes enabled)

Changes

Configuration (lib/config.go)

• Added DefaultIndexOrdersByAddresses constant
• Added IndexOrdersByAddresses field to StateMachineConfig

State Machine (fsm/swap.go)

• SetOrder: Conditionally creates seller/buyer secondary indexes based on config
• cleanupStaleBuyerIndex: Skips cleanup when indexing is disabled
• DeleteOrder: Conditionally deletes seller/buyer secondary indexes based on config

RPC Endpoint (cmd/rpc/query.go)

• Orders: Returns descriptive error when address-based filtering is requested but indexing is disabled