Restructure go project (#2356)

* Move main to cmd
* Move api to internal
* Move logger and manager to internal
* Move shell hiding code to separate package
* Decouple job from desktop and utils
* Decouple session from config
* Move static into internal
* Decouple config from dlna
* Move desktop to internal
* Move dlna to internal
* Decouple remaining packages from config
* Move config into internal
* Move jsonschema and paths to models
* Make ffmpeg functions private
* Move file utility methods into fsutil package
* Move symwalk into fsutil
* Move single-use util functions into client package
* Move slice functions to separate packages
* Add env var to suppress windowsgui arg
* Move hash functions into separate package
* Move identify to internal
* Move autotag to internal
* Touch UI when generating backend

internal/manager/task.go

@@ -0,0 +1,8 @@
+package manager
+
+import "context"
+
+type Task interface {
+	Start(context.Context)
+	GetDescription() string
+}