Fix "invalid cross-device link" error when running on a different filesystem (#1769)

* fix cross-device rename errors

* fallback to copy instead of always using it

* use tmp dir in data folder

* recreate tmp dir at startup

config/config.go

@@ -13,6 +13,8 @@ var DatabaseFilePath = "data/owncast.db"
 // LogDirectory is the path to various log files.
 var LogDirectory = "./data/logs"
 
+var TempDir = "./data/tmp"
+
 // EnableDebugFeatures will print additional data to help in debugging.
 var EnableDebugFeatures = false