feat(uploads): choose the language of a recording; record it, show it, carry it to the engines (#61)

Form field (Swedish preselected, Other = auto) read before the file part and refused
before anything is spooled if outside the closed set; stored on the row (migration 021,
CHECK constraint, default sv for history); carried on the Job and the worker's context;
shown on the status page. Feature scenarios and the coverage map are updated, and
ADR-033/034 amended.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/adapters/store/uploaded_transcripts_delete_test.go

@@ -42,7 +42,7 @@ func TestDeleteUpload_RefusesAnUploadThatIsStillQueuedOrTranscribingAndKeepsTheR
 	s := newStore(t)
 	ctx := context.Background()
 	queued := startedUpload(t, s)
-	running, err := s.CreateUpload(ctx, userA, "running", false)
+	running, err := s.CreateUpload(ctx, userA, "running", domain.LangSwedish, false)
 	require.NoError(t, err)
 	require.NoError(t, s.StartTranscribing(ctx, userA, running))