Do not panic on failure to acquire connections to store events (#4132)

# Description
During a particularly bad period of volatility we failed to acquire a DB
connection on time which lead to a panic

<details><summary>Partial Stacktrace</summary>
<p>

```
1770314825856	2026-02-05T18:07:05.856Z	2026-02-05T18:07:03.033Z ERROR observe::tracing: thread 'tokio-runtime-worker' panicked at /src/crates/autopilot/src/infra/persistence/mod.rs:301:54:
1770314825856	2026-02-05T18:07:05.856Z	failed to acquire tx: PoolTimedOut
1770314825856	2026-02-05T18:07:05.856Z	stack backtrace:
1770314825856	2026-02-05T18:07:05.856Z	   0: observe::tracing::tracing_panic_hook
1770314825856	2026-02-05T18:07:05.856Z	             at ./src/crates/observe/src/tracing.rs:187:21
1770314825856	2026-02-05T18:07:05.856Z	   1: <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call
1770314825856	2026-02-05T18:07:05.856Z	             at ./rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/alloc/src/boxed.rs:2220:9
1770314825856	2026-02-05T18:07:05.856Z	   2: observe::panic_hook::install::{{closure}}
1770314825856	2026-02-05T18:07:05.856Z	             at ./src/crates/observe/src/panic_hook.rs:14:9
1770314825856	2026-02-05T18:07:05.856Z	   3: <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call
1770314825856	2026-02-05T18:07:05.856Z	             at ./rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/alloc/src/boxed.rs:2220:9
1770314825856	2026-02-05T18:07:05.856Z	   4: std::panicking::panic_with_hook
1770314825856	2026-02-05T18:07:05.856Z	             at ./rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/std/src/panicking.rs:833:13
1770314825856	2026-02-05T18:07:05.856Z	   5: std::panicking::panic_handler::{{closure}}
1770314825856	2026-02-05T18:07:05.856Z	             at ./rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/std/src/panicking.rs:698:13
1770314825856	2026-02-05T18:07:05.856Z	   6: std::sys::backtrace::__rust_end_short_backtrace
1770314825856	2026-02-05T18:07:05.856Z	             at ./rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/std/src/sys/backtrace.rs:176:18
1770314825856	2026-02-05T18:07:05.856Z	   7: __rustc::rust_begin_unwind
1770314825856	2026-02-05T18:07:05.856Z	             at ./rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/std/src/panicking.rs:689:5
1770314825856	2026-02-05T18:07:05.856Z	   8: core::panicking::panic_fmt
1770314825856	2026-02-05T18:07:05.856Z	             at ./rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/core/src/panicking.rs:80:14
1770314825856	2026-02-05T18:07:05.856Z	   9: core::result::unwrap_failed
1770314825856	2026-02-05T18:07:05.856Z	             at ./rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/core/src/result.rs:1867:5
1770314825856	2026-02-05T18:07:05.856Z	  10: core::result::Result<T,E>::expect
1770314825856	2026-02-05T18:07:05.856Z	             at ./rustc/254b59607d4417e9dffbc307138ae5c86280fe4c/library/core/src/result.rs:1185:23
1770314825856	2026-02-05T18:07:05.856Z	  11: autopilot::infra::persistence::Persistence::store_order_events::{{closure}}
1770314825856	2026-02-05T18:07:05.856Z	             at ./src/crates/autopilot/src/infra/persistence/mod.rs:301:54
```

</p>
</details> 

# Changes

- [ ] Remove the panic
- [ ] Log on error and continue

## How to test
NA

Author: jmg-duarte

crates/autopilot/src/infra/persistence/mod.rs

@@ -298,8 +298,17 @@ impl Persistence {
         let order_uids = order_uids.into_iter().collect();
         tokio::spawn(
             async move {
-                let mut tx = db.pool.acquire().await.expect("failed to acquire tx");
-                store_order_events(&mut tx, order_uids, label, Utc::now()).await;
+                match db.pool.acquire().await {
+                    Ok(mut tx) => {
+                        store_order_events(&mut tx, order_uids, label, Utc::now()).await;
+                    }
+                    Err(err) => {
+                        tracing::error!(
+                            ?err,
+                            "failed to acquire a connection to store order events!"
+                        );
+                    }
+                };
             }
             .instrument(tracing::Span::current()),
         );

crates/database/src/orders.rs

@@ -964,6 +964,7 @@ pub async fn user_orders_with_quote(
         FROM   orders o
         WHERE  o.cancellation_timestamp IS NULL
             AND o.true_valid_to >= $1
+            AND NOT EXISTS (SELECT 1 FROM ethflow_refunds r WHERE r.order_uid = o.uid)
             AND NOT EXISTS (SELECT 1 FROM invalidations i WHERE i.order_uid = o.uid)
             AND NOT EXISTS (SELECT 1 FROM onchain_order_invalidations oi WHERE oi.uid = o.uid)
             AND NOT EXISTS (SELECT 1 FROM onchain_placed_orders op WHERE op.uid = o.uid AND op.placement_error IS NOT NULL)