Tighter filter on all solvable orders query

[MartinquaXD]

Description

Forgot that I already hit merge when ready on #4129 so I was to slow to merge the same optimization for the open orders query.

[gemini-code-assist]

Code Review

The added filter for ethflow_refunds is correct. However, it creates a redundant join in the solvable_orders query, impacting performance. A fix is suggested in the review comment.

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crates/database/src/orders.rs (732)

This filter makes the LEFT JOIN on ethflow_refunds at line 806 redundant. Since live_orders no longer contains refunded orders, tx_hash from ethflow_refunds will always be NULL.

To improve clarity and performance, remove the unnecessary join by changing lines 803-808.

-    LEFT JOIN LATERAL (
-        SELECT ROW(tx_hash, eo.valid_to) AS ethflow_data
-        FROM   ethflow_orders  eo
-        LEFT JOIN ethflow_refunds r ON r.order_uid = eo.uid
-        WHERE  eo.uid = lo.uid
-        ) ed ON TRUE
+    LEFT JOIN LATERAL (
+        SELECT ROW(NULL::bytea, eo.valid_to) AS ethflow_data
+        FROM   ethflow_orders  eo
+        WHERE  eo.uid = lo.uid
+        ) ed ON TRUE