Fix flaky transcription duration assertion in CI.

Use integer timestamps for duration and pin the test clock to a whole second so SQLite round-trips stay stable.

app/Models/Recording.php

@@ -434,7 +434,7 @@ class Recording extends Model
         $startedAt = $this->transcription_started_at;
         $durationSeconds = $startedAt === null
             ? null
-            : max(0, (int) round($startedAt->diffInSeconds($finishedAt)));
+            : max(0, $finishedAt->getTimestamp() - $startedAt->getTimestamp());
 
         $this->forceFill([
             'transcript' => $text,

tests/Feature/RecordingUploadTest.php

@@ -210,7 +210,7 @@ class RecordingUploadTest extends TestCase
 
         Transcription::fake(['Hello from the recorder.']);
 
-        $this->freezeTime();
+        $this->travelTo(now()->startOfSecond());
 
         $recording = Recording::query()->create([
             'user_id' => $this->user->id,
@@ -231,6 +231,10 @@ class RecordingUploadTest extends TestCase
         $this->assertSame(100, $recording->transcription_percent);
         $this->assertSame('Transcription complete', $recording->transcription_progress);
         $this->assertNotNull($recording->transcribed_at);
+        $this->assertSame(
+            $recording->transcribed_at->getTimestamp() - $recording->transcription_started_at->getTimestamp(),
+            $recording->transcription_duration_seconds,
+        );
         $this->assertSame(42, $recording->transcription_duration_seconds);
         $this->assertSame('42s', $recording->transcriptionStatusPayload()['transcription_duration_human']);
     }