Fixes issue where identity names were not saved when switching between
multiple identities. Names were being saved to master settings instead
of user-specific settings.

Changes:
- UserNameDialog: Load/save names from/to user-specific settings
- NewEditAccountView: Save names to user-specific settings for active DID
- Both components now use $accountSettings() and $saveUserSettings()
  instead of $settings() and $updateSettings()

Each identity now properly retains their assigned name when switching
between identities. Previously only "User Zero" would show their name
due to using master settings instead of per-identity settings.

Fixes: Identity name persistence across identity switches

@@ -117,0 +118,4 @@
+      // Save to user-specific settings for the current identity
+      await this.$saveUserSettings(activeDid, {
+        firstName: this.givenName,
+        lastName: "", // deprecated, pre v 0.1.3