fix: widget_test.dart is a default counter test and will always fail

## Description

The file `test/widget_test.dart` is the default Flutter counter app test from `flutter create`. It tests for a counter widget (`find.text('0')`, `find.byIcon(Icons.add)`) that does not exist in DocPilot.

This test will **always fail** because DocPilot is a transcription app, not a counter app. This makes any CI pipeline unreliable.

## Current Content

```dart
testWidgets('Counter increments smoke test', (WidgetTester tester) async {
await tester.pumpWidget(const MyApp());
expect(find.text('0'), findsOneWidget); // DocPilot has no '0' text
expect(find.text('1'), findsNothing);
await tester.tap(find.byIcon(Icons.add)); // DocPilot has no '+' icon
...
});
```

## Expected Fix

Replace with a basic smoke test that verifies DocPilot renders its main UI elements (app title, microphone button).