persist confirm-tx view across popup close/reopen (closes #77)

Add confirm-tx to RESTORABLE_VIEWS and save pendingTx in
state.viewData so the confirmation screen survives the popup
lifecycle. On restore, re-render the full confirmation view
including gas estimate.

src/popup/index.js

@@ -74,6 +74,7 @@ const RESTORABLE_VIEWS = new Set([
     "receive",
     "settings",
     "settings-addtoken",
+    "confirm-tx",
     "transaction",
     "success-tx",
     "error-tx",
@@ -127,6 +128,13 @@ function restoreView() {
         case "settings-addtoken":
             settingsAddToken.show();
             break;
+        case "confirm-tx":
+            if (state.viewData && state.viewData.pendingTx) {
+                confirmTx.restore();
+            } else {
+                fallbackView();
+            }
+            break;
         case "transaction":
             if (state.viewData && state.viewData.tx) {
                 transactionDetail.render();

src/popup/views/confirmTx.js

@@ -38,6 +38,13 @@ const EXT_ICON =
 
 let pendingTx = null;
 
+function restore() {
+    const d = state.viewData;
+    if (d && d.pendingTx) {
+        show(d.pendingTx);
+    }
+}
+
 function etherscanTokenLink(address) {
     return `https://etherscan.io/token/${address}`;
 }
@@ -217,6 +224,7 @@ function show(txInfo) {
     // Gas estimate — show placeholder then fetch async
     $("confirm-fee").classList.remove("hidden");
     $("confirm-fee-amount").textContent = "Estimating...";
+    state.viewData = { pendingTx: txInfo };
     showView("confirm-tx");
 
     estimateGas(txInfo);
@@ -347,4 +355,4 @@ function init(ctx) {
     });
 }
 
-module.exports = { init, show };
+module.exports = { init, show, restore };