fix(account-snapshot): treat timeout/http5xx as transient fallback failures

Co-authored-by: genichin <4282227+genichin@users.noreply.github.com>

trex_core/application/account_snapshot.py

@@ -217,7 +217,7 @@ class AccountSnapshotService:
         try:
             return self._broker.get_balance()
         except BrokerBalanceError as exc:
-            if exc.code != "transport_failed":
+            if exc.code not in {"transport_failed", "timeout", "http_5xx"}:
                 raise AccountSnapshotUnavailable(
                     "live_read_failed", detail_code=exc.code
                 ) from None
@@ -253,7 +253,7 @@ class AccountSnapshotService:
         reserved_cash: float = 0.0,
     ) -> Optional[str]:
         """Return a stable rejection reason, or None when bounded admission passes."""
-        if self._last_cash_error not in {None, "transport_failed"}:
+        if self._last_cash_error not in {None, "transport_failed", "timeout", "http_5xx"}:
             return "account_snapshot_unavailable"
         try:
             snapshot = self._load_current()