feat(ui): clamp recent-activity lists to the 4 most recent

The overview "Recent Transactions" and the send tab "Recent Sends" lists showed
every matching transaction in a scroll region. Cap them at the 4 most recent
(state.transactions is sorted newest-first, so a simple head-limit). The receive
"Recent Received" list gets the same clamp in the Tier-1 robustness commit
(same file as the QR fix).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ui/windows/balance_components.cpp

@@ -786,7 +786,7 @@ void RenderSharedRecentTx(App* app, float recentH, float availW, float hs, float
         ImGuiWindowFlags_NoBackground);
 
     const auto& txs = state.transactions;
-    int count = (int)txs.size();
+    int count = std::min(4, (int)txs.size());  // show only the 4 most recent (state.transactions is newest-first)
 
     if (count == 0) {
         Type().textColored(TypeStyle::Caption, OnSurfaceDisabled(), TR("no_transactions_yet"));

src/ui/windows/send_tab.cpp

@@ -1025,6 +1025,7 @@ static void RenderRecentSends(const WalletState& state, float width, ImFont* cap
         if (tx.type != "send" && tx.type != "shield") continue;
         sends.push_back(&tx);
     }
+    if (sends.size() > 4) sends.resize(4);  // show only the 4 most recent (newest-first)
 
     float listH = std::max(rowH, ImGui::GetContentRegionAvail().y);