test: the test suite exits on its own, without --forceExit (closes #585)

Some tests left timers running when they ended, and --forceExit hid them.

- Six background test files leave an approval pending, so the background's
  20-second timer ran forever. Each file now stubs that timer, as two blocks
  in tests/backgroundApproval.test.js already did.
- Five popup test files show a flash message, and its timer outlived the
  test. They now run on fake timers.

Both test scripts in package.json drop --forceExit.

Model: opus-5-5

tests/sendMax.test.js

@@ -277,14 +277,18 @@ async function review() {
 
 // show() starts the fee estimate without awaiting it; this lets it settle.
 async function settle() {
-    for (let i = 0; i < 10; i++) await new Promise((r) => setTimeout(r, 0));
+    for (let i = 0; i < 10; i++) await jest.advanceTimersByTimeAsync(0);
 }
 
 function canSend() {
     return !el("btn-confirm-send").disabled;
 }
 
+// showFlash() starts a timer that clears the message two seconds later. Each
+// test here runs on fake timers and drops them in afterEach, so that timer
+// never outlives the test.
 beforeEach(() => {
+    jest.useFakeTimers();
     elements.clear();
     log.errorf.mockClear();
     pageClosed = new AbortController();
@@ -297,6 +301,10 @@ beforeEach(() => {
     mockNode.broadcast = [];
 });
 
+afterEach(() => {
+    jest.useRealTimers();
+});
+
 describe("Max on an ETH send", () => {
     test("fills in the exact balance minus the fee reserve", async () => {
         await refreshWith(BALANCE_WEI);