fix: normalize snapshot read failures to unavailable in slots RPC path

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

trex_core/application/account_snapshot.py

@@ -49,6 +49,7 @@ class AccountSnapshotUnavailable(RuntimeError):
         "account_mismatch",
         "expired",
         "live_read_failed",
+        "read_failed",
     })
 
     def __init__(self, code: str) -> None:
@@ -189,7 +190,15 @@ class AccountSnapshotService:
         account_hash = self._broker.account_scope_hash()
         if not account_hash:
             raise AccountSnapshotUnavailable("account_mismatch")
-        snapshot = self._store.load(account_hash)
+        try:
+            snapshot = self._store.load(account_hash)
+        except Exception as exc:
+            _log.warning(
+                "account snapshot load failed: account_hash=%s",
+                account_hash,
+                exc_info=True,
+            )
+            raise AccountSnapshotUnavailable("read_failed") from exc
         if snapshot is None or snapshot.account_hash != account_hash:
             raise AccountSnapshotUnavailable("account_mismatch")
         return snapshot