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/backup_wallet_dialog.cpp

@@ -120,6 +120,7 @@ void BackupWalletDialog::render(App* app)
                         bool success = false;
                         std::string statusMsg;
                         try {
+                            rpc::RPCClient::TraceScope trace("Settings / Backup wallet");
                             rpc->call("backupwallet", json::array({dest}));
                             // Check if file was created
                             if (fs::exists(dest)) {