perf(history): add a transactions revision counter to WalletState

WalletState had no change signal for its transaction list, so a UI
cache had to fingerprint all N transactions every frame to notice an
update. It now carries tx_revision, a counter that only increases;
clear() on disconnect bumps it instead of resetting it, so a cache
built before a reconnect or wallet switch can never match again.

- Every writer of the list bumps it: the full-node refresh, loading the
  cached history, adding, completing and removing a pending send, a
  mining-address relabel, the lite refresh and the screenshot demo
  rows.
- The full-node refresh and the lite refresh (every ~2 s) swap in the
  new list only when it differs field by field, the amount compared
  bit-exactly because -0.0 and +0.0 print differently. An unchanged
  refresh keeps the list and the revision; the compare costs O(N) per
  refresh, not per frame.

Nothing reads the counter yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/services/network_refresh_service.cpp

@@ -1911,7 +1911,7 @@ void NetworkRefreshService::applyTransactionRefreshResult(WalletState& state,
                                                           TransactionRefreshResult&& result,
                                                           std::time_t updatedAt)
 {
-    state.transactions = std::move(result.transactions);
+    state.setTransactionsIfChanged(std::move(result.transactions));   // bumps tx_revision only on a real change
     state.last_tx_update = updatedAt;
     cacheUpdate.lastTxBlockHeight = result.blockHeight;