Add user PIN protection (#719)

## Description
Adds (back) the ability to set a per-user PIN. This is required to
switch to the user. If the user has a PIN, this overrides and ignores
the "Sign in automatically" setting for that user.

The PIN consists of any combination of D-Pad directional buttons. If you
forget the PIN, you can click the button to login via the server instead
(ie QuickConnect or username/password) which will also remove the PIN so
you can set a new one if desired.

### Related issues
Closes #268 
Replaces #398
Related to #321 & #356

### Screenshots
![enter_pin
Large](https://github.com/user-attachments/assets/aa25364d-1266-410d-846e-8dc32c56a794)

app/src/main/java/com/github/damontecres/wholphin/preferences/AppPreference.kt

@@ -932,8 +932,7 @@ val basicPreferences =
             title = R.string.profile_specific_settings,
             preferences =
                 listOf(
-                    // TODO PIN-related
-                    // AppPreference.RequireProfilePin,
+                    AppPreference.RequireProfilePin,
                     AppPreference.UserPinnedNavDrawerItems,
                 ),
         ),