add conversion phase & progress metrics, timeout heuristics

proto/officeconvertapi/v1/conversion.proto

@@ -33,6 +33,16 @@ enum ConversionStatus {
   CONVERSION_STATUS_FAILED = 4;
 }
 
+// ConversionPhase represents the active stage for a running conversion.
+enum ConversionPhase {
+  CONVERSION_PHASE_UNSPECIFIED = 0;
+  CONVERSION_PHASE_INACTIVE = 1;
+  CONVERSION_PHASE_EXTRACTING_NOTES = 2;
+  CONVERSION_PHASE_PPTX_TO_PDF = 3;
+  CONVERSION_PHASE_PDF_TO_IMAGES = 4;
+  CONVERSION_PHASE_UPLOADING_RESULTS = 5;
+}
+
 // Slide contains extracted notes and the rendered image URL for one slide.
 message Slide {
   int32 index = 1;
@@ -84,6 +94,9 @@ message GetConversionStatusResponse {
   ConversionStatus status = 2;
   string error_message = 3;
   google.protobuf.Timestamp updated_at = 4;
+  ConversionPhase phase = 5;
+  int32 current_progress = 6;
+  int32 max_progress = 7;
 }
 
 // GetSlideDeckRequest fetches a completed deck.