Always attempt automatic backup creation

- Defaults to every 12 hours
- Minimum number of backups is now 2, just to offer some level of redundancy in case something happens
- If it's missing storage permissions, it'll fail but that's the user's loss if they somehow haven't granted that permission yet

app/src/main/java/eu/kanade/tachiyomi/Migrations.kt

@@ -284,6 +284,15 @@ object Migrations {
                     remove("library_sorting_ascending")
                 }
             }
+            if (oldVersion < 84) {
+                if (preferences.numberOfBackups().get() == 1) {
+                    preferences.numberOfBackups().set(2)
+                }
+                if (preferences.backupInterval().get() == 0) {
+                    preferences.backupInterval().set(12)
+                    BackupCreatorJob.setupTask(context)
+                }
+            }
             return true
         }