feat(wallet): persist history and surface pending sends

Add an encrypted SQLite transaction history cache with cached tip metadata and
per-address shielded scan progress so startup and full refreshes avoid
re-scanning every z-address while still invalidating on wallet/address/rescan
changes.

Improve wallet history loading by paging transparent transactions, preserving
cached shielded and sent rows, keeping recent/unconfirmed activity visible, and
classifying mining-address receives. Show z_sendmany opid sends immediately in
History and Overview, pin pending rows through refreshes, and apply optimistic
address/balance debits until opids resolve.

Add timestamped RPC console tracing by source/method without logging params or
results, reduce redundant refresh/RPC calls, and cache Explorer recent block
summaries in SQLite.

Expand focused tests for transaction cache encryption, scan-progress
persistence/invalidation, history preservation, operation-status parsing,
pending send visibility, and Explorer/RPC refresh behavior.

src/ui/windows/settings_window.cpp

@@ -429,6 +429,7 @@ void RenderSettingsWindow(App* app, bool* p_open)
 
             if (material::StyledButton(TR("test_connection"), ImVec2(0,0), S.resolveFont("button"))) {
                 if (app->rpc()) {
+                    rpc::RPCClient::TraceScope trace("Settings / Test connection");
                     app->rpc()->getInfo([](const nlohmann::json& result, const std::string& error) {
                         if (error.empty()) {
                             std::string version = result.value("version", "unknown");