Add option to require server login for user profile (#1367)

## Description
This PR adds a new method of protecting a user profile when switching to
it: server login. When enabled, switching to the user requires
authenticating with the server again via Quick Connect or username &
password. This is basically the same as the official client.

### Related issues
Closes #321
Related to #1330 - might cause merge conflicts
Related to #1287 - definitely causes merge conflicts

### Testing
Emulator with various uses cases including auto sign-in, switching
between server login & PIN protection, and removing the protection

## Screenshots
N/A, the login looks identical as adding a new user

## AI or LLM usage
None

app/src/main/java/com/github/damontecres/wholphin/MainActivity.kt

@@ -434,8 +434,11 @@ class MainActivityViewModel
                     appUpgradeHandler.copySubfont(false)
                     val prefs =
                         preferences.data.firstOrNull() ?: AppPreferences.getDefaultInstance()
-                    val userHasPin = serverRepository.currentUser.value?.hasPin == true
-                    if (prefs.signInAutomatically && !userHasPin) {
+                    val allowAutoSignIn =
+                        serverRepository.currentUser.value?.let {
+                            !it.hasPin && !it.requireLogin
+                        } == true
+                    if (prefs.signInAutomatically && allowAutoSignIn) {
                         val current =
                             serverRepository.restoreSession(
                                 prefs.currentServerId?.toUUIDOrNull(),