Garmin: Add workaround for missing next page id on new sync protocol

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/garmin/FileSyncServiceHandler.kt

@@ -89,6 +89,15 @@ class FileSyncServiceHandler(val deviceSupport: GarminSupport) {
             deviceSupport.addFileToDownloadList(file)
         }
 
+        // #5461 - some watches to not send the next page ID
+        // however, from previous logs, it always seems to match the max seen across all sent items, so attempt
+        // to fallback to that as a workaround so we can fetch the subsequent files
+        if (fileListResponse.nextPageId == 0) {
+            nextPageId = fileListResponse.fileList
+                .mapNotNull { it.pageId }
+                .maxOrNull() ?: 0
+        }
+
         return null
     }
 

app/src/main/proto/garmin/gdi_file_sync_service.proto

@@ -56,8 +56,10 @@ message FileListRequest {
 
 message FileListResponse {
   optional uint32 unk1 = 1; // 0
+  optional uint32 unk2 = 2; // 2 on venu 4
   optional uint32 next_page_id = 3; // 33737, incrementiong
   repeated File file = 4;
+  optional uint32 unk6 = 6; // 1 on venu 4
 }
 
 message File {
@@ -65,6 +67,8 @@ message File {
   optional FileType type = 2;
   optional uint32 size = 3;
   optional uint32 page_id = 5; // 33652, 33653, ... incrementing
+  optional uint32 unk4 = 4; // 0 on venu 4
+  optional uint32 unk6 = 6; // 2 on venu 4
 }
 
 message FileId {