feat(config): TAPIR_TRANSCRIBE_ENGINE_TIMEOUT, default 25 minutes (review F4)

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

internal/config/uploads.go

@@ -28,6 +28,10 @@ type UploadConfig struct {
 	// TranscribeTimeout bounds one job (conversion + transcription); a 90 minute
 	// recording took ~7.5 minutes on iguana.
 	TranscribeTimeout time.Duration
+	// TranscribeEngineTimeout bounds ONE engine call, so a wedged engine fails while the
+	// job is still alive and the fallback (or the other engine) can take over. The job
+	// timeout alone cannot do that (ADR-035 review).
+	TranscribeEngineTimeout time.Duration
 	// UploadTmpDir is where uploads are spooled and converted. Audio is deleted
 	// after transcription, so this holds at most the in-flight files.
 	UploadTmpDir string
@@ -62,6 +66,7 @@ const (
 	defaultTranscribeModel         = "iguana/kb-whisper"
 	defaultTranscribeFallbackModel = "berget/kb-whisper"
 	defaultTranscribeTimeout       = 60 * time.Minute
+	defaultTranscribeEngineTimeout = 25 * time.Minute
 	defaultMaxUploadedChars        = 90000
 	defaultUploadChatModel         = "iguana/gemma4-26b"
 )
@@ -107,6 +112,15 @@ func loadUploadConfig() (UploadConfig, error) {
 	}
 	u.TranscribeTimeout = timeout
 
+	engineTimeout, err := durationOr("TAPIR_TRANSCRIBE_ENGINE_TIMEOUT", defaultTranscribeEngineTimeout)
+	if err != nil {
+		return UploadConfig{}, err
+	}
+	if engineTimeout <= 0 {
+		return UploadConfig{}, fmt.Errorf("config: TAPIR_TRANSCRIBE_ENGINE_TIMEOUT must be positive, got %v", engineTimeout)
+	}
+	u.TranscribeEngineTimeout = engineTimeout
+
 	if v := os.Getenv("TAPIR_RECONCILE_CHECK_ORDER"); v != "" {
 		on, err := strconv.ParseBool(v)
 		if err != nil {