Keep category orders unique while reordering

Reordering first moves every category to a temporary negative position, then assigns the final ones, so two categories never share a position mid-update. Deleting a category no longer renumbers the system category.

data/src/main/java/tachiyomi/data/category/CategoryRepositoryImpl.kt

@@ -77,6 +77,9 @@ class CategoryRepositoryImpl(
 
     override suspend fun updateAllOrders(orderedIds: List<Long>) {
         database.transaction {
+            orderedIds.forEachIndexed { index, categoryId ->
+                database.categoriesQueries.updateOrder(order = -index - 2L, categoryId = categoryId)
+            }
             orderedIds.forEachIndexed { index, categoryId ->
                 database.categoriesQueries.updateOrder(order = index.toLong(), categoryId = categoryId)
             }