[misc] Move shared components to shared directory (#4286)

Moved the following directories:

```
  - management/client → shared/management/client
  - management/domain → shared/management/domain
  - management/proto → shared/management/proto
  - signal/client → shared/signal/client
  - signal/proto → shared/signal/proto
  - relay/client → shared/relay/client
  - relay/auth → shared/relay/auth
```

and adjusted import paths

shared/relay/auth/doc.go

@@ -0,0 +1,26 @@
+/*
+Package auth manages the authentication process with the relay server.
+
+Key Components:
+
+Validator: The Validator interface defines the Validate method. Any type that provides this method can be used as a
+Validator.
+
+Methods:
+
+Validate(func() hash.Hash, any): This method is defined in the Validator interface and is used to validate the authentication.
+
+Usage:
+
+To create a new AllowAllAuth validator, simply instantiate it:
+
+	validator := &allow.Auth{}
+
+To validate the authentication, use the Validate method:
+
+	err := validator.Validate(sha256.New, any)
+
+This package provides a simple and effective way to manage authentication with the relay server, ensuring that the
+peers are authenticated properly.
+*/
+package auth