feat(app): transaction detail overlay with full on-chain data

Double-clicking a history row opens an in-app overlay (same pattern as
address/server/settings overlays) that shows all available data for a
transaction. The overlay appears immediately with a spinner; data is
fetched from the server in the background and rendered once ready.
Backdrop tap and Esc close it; a pending fetch is cancelled.

New Core type — TransactionInspector (Core/Wallet/):
- FetchAsync() downloads the raw tx, all parent txs (parallel requests,
  one round-trip instead of N sequential), and the block header
- Reconstructs inputs (amounts, addresses, is-mine), outputs, fee,
  virtual size, RBF flag, block timestamp, confirmations

New App types:
- TransactionDetails record: full parsed data (fee, net, I/O lists,
  counterparty addresses, coinbase detection…)
- TransactionDetailsViewModel: pre-formats all strings in the current
  locale and unit (status, date, signed amounts, sat/vB rate…)
- TxIoRow record: one row in the input/output tables
- MineColorConverter: bool → brush (MediumSeaGreen for own addresses)

ViewModel changes:
- ShowTransactionDetailsAsync / CloseTransactionDetailsCommand
- BuildTransactionDetailsAsync (also public for future RBF/CPFP use)
- CancellationTokenSource so opening a new tx cancels the previous fetch
- All server work runs on Task.Run to keep the UI thread free

XAML: history rows get DoubleTapped handler, Hand cursor, hint label,
txid now uses TextTrimming instead of SelectableTextBlock.

i18n: 24 new tx.* / history.hint keys in all 6 languages.

src/App/Views/MainWindow.axaml.cs

@@ -37,6 +37,23 @@ public partial class MainWindow : Window
             vm.OpenFromPath(path);
     }
 
+    private void OnHistoryRowDoubleTapped(object? sender, TappedEventArgs e)
+    {
+        if (sender is not ListBox lb || DataContext is not MainWindowViewModel vm) return;
+        if (lb.SelectedItem is not HistoryRow row) return;
+
+        // Overlay in-app: appare subito con lo spinner, i dati arrivano dal
+        // server in background. Niente top-level window (lenta da aprire/chiudere).
+        _ = vm.ShowTransactionDetailsAsync(row.Txid);
+    }
+
+    private void OnTxDetailsOverlayBackdropTapped(object? sender, TappedEventArgs e)
+    {
+        if (!ReferenceEquals(e.Source, sender)) return;
+        if (DataContext is MainWindowViewModel vm)
+            vm.CloseTransactionDetailsCommand.Execute(null);
+    }
+
     private void OnAddressListTapped(object? sender, TappedEventArgs e)
     {
         if (DataContext is not MainWindowViewModel vm || vm.SelectedAddressRow is not { } row)
@@ -115,6 +132,7 @@ public partial class MainWindow : Window
     {
         if (e.Key == Key.Escape && DataContext is MainWindowViewModel vm)
         {
+            if (vm.IsTxDetailsOpen) { vm.CloseTransactionDetailsCommand.Execute(null); e.Handled = true; return; }
             if (vm.AddressInfo is not null) { vm.AddressInfo = null; e.Handled = true; return; }
             if (vm.IsServerSettingsOpen) { vm.IsServerSettingsOpen = false; e.Handled = true; return; }
             if (vm.IsSettingsOpen) { vm.IsSettingsOpen = false; e.Handled = true; return; }