feat(session): track user language + preferences

Mirrors the existing name/avatar/id fields — Settings' Preferences page
needs somewhere to read current values from and applyUpdatedProfile
already refreshes everything else on save.

Outpost/Root/SessionStore.swift

@@ -15,6 +15,8 @@ final class SessionStore {
     var userName: String?
     var userEmail: String?
     var userAvatarURL: URL?
+    var userLanguage: String?
+    var userPreferences: OutlineUserPreferences?
     var teamName: String?
     var teamAvatarURL: URL?
     private(set) var apiClient: OutlineAPIClient?
@@ -73,6 +75,8 @@ final class SessionStore {
         userName = nil
         userEmail = nil
         userAvatarURL = nil
+        userLanguage = nil
+        userPreferences = nil
         teamName = nil
         teamAvatarURL = nil
         apiClient = nil
@@ -95,6 +99,8 @@ final class SessionStore {
         userId = user.id
         userName = user.name
         userAvatarURL = user.avatarUrl.flatMap { URL(string: $0, relativeTo: serverURL)?.absoluteURL }
+        userLanguage = user.language
+        userPreferences = user.preferences
     }
 
     private func apply(user: OutlineUser, team: OutlineTeam, serverURL: URL) {
@@ -105,6 +111,8 @@ final class SessionStore {
         // (e.g. `/api/files.get?key=...`) for avatarUrl — resolve against the
         // configured server so relative paths don't fail as "unsupported URL".
         userAvatarURL = user.avatarUrl.flatMap { URL(string: $0, relativeTo: serverURL)?.absoluteURL }
+        userLanguage = user.language
+        userPreferences = user.preferences
         teamName = team.name
         teamAvatarURL = team.avatarUrl.flatMap { URL(string: $0, relativeTo: serverURL)?.absoluteURL }
     }