Fix devnet1 OrdersGateway: stale default broke EIP-712 signing (PRO-164)

The non-mainnet default verifyingContract (0x5a0a...) is the older reya_cronos
deployment and is stale for devnet1, where the live OrdersGateway is
0x7Ec89E555c771D2B5939aBE5C4E4291852633D4D — confirmed by reya-devops
(ORDERS_GATEWAY_PROXY_ADDRESS across every devnet1 service incl. ws-exec) and
the reya-deployments reya_devnet fork test. With REYA_ORDERS_GATEWAY unset, the
SDK signed against the wrong contract and the matching engine rejected every
order with an opaque "invalid signature" error.

- config.py: point the non-mainnet baked-in default at the devnet1 gateway.
- .env.example: set REYA_ORDERS_GATEWAY for devnet1 (+ commented mainnet value)
  so following the example works out of the box.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: arturbeg

.env.example

@@ -3,12 +3,17 @@ CHAIN_ID=89346162
 REYA_WS_URL="wss://websocket-devnet.reya-cronos.network/"
 REYA_WS_EXEC_URL="wss://ws-exec-devnet.reya-cronos.network"
 REYA_API_URL="https://api-devnet.reya-cronos.network/v2"
+# OrdersGateway proxy = the EIP-712 verifyingContract. Set this on devnet1: the
+# baked-in fallback is stale here, so leaving it unset makes the matching engine
+# reject every order with an opaque "invalid signature" error.
+REYA_ORDERS_GATEWAY="0x7Ec89E555c771D2B5939aBE5C4E4291852633D4D"
 
 ### Reya Network (mainnet)
 #CHAIN_ID=1729
 #REYA_WS_URL="wss://ws.reya.xyz/"
 #REYA_WS_EXEC_URL="wss://ws-exec.reya.xyz"
 #REYA_API_URL="https://api.reya.xyz/v2"
+#REYA_ORDERS_GATEWAY="0xfc8c96be87da63cecddbf54abfa7b13ee8044739"
 
 ### Staging (uses mainnet chain ID 1729)
 #CHAIN_ID=1729

sdk/reya_rest_api/config.py

@@ -66,7 +66,7 @@ def default_orders_gateway_address(self) -> str:
         if self.is_mainnet:
             return "0xfc8c96be87da63cecddbf54abfa7b13ee8044739"  # Mainnet address
         else:
-            return "0x5a0ac2f89e0bdeafc5c549e354842210a3e87ca5"  # Testnet address
+            return "0x7Ec89E555c771D2B5939aBE5C4E4291852633D4D"  # devnet1 (perpOB testnet)
 
     @classmethod
     def from_env(cls) -> "TradingConfig":