Rework avatars.

Now we have a concept of an avatar at the server, realm, and scene level
and we have the groundwork for a realm store. New uesrs no longer props,
they get a default avatar. New system supports gender
{male,female,neutral} and {child,adult}.

crates/chattyness-user-ui/src/api/routes.rs

@@ -31,6 +31,10 @@ pub fn api_router() -> Router<AppState> {
             "/auth/register-guest",
             axum::routing::post(auth::register_guest),
         )
+        .route(
+            "/auth/preferences",
+            axum::routing::put(auth::update_preferences),
+        )
         // Realm routes (READ-ONLY)
         .route("/realms", get(realms::list_realms))
         .route("/realms/{slug}", get(realms::get_realm))
@@ -62,6 +66,17 @@ pub fn api_router() -> Router<AppState> {
             "/realms/{slug}/avatar/slot",
             axum::routing::put(avatars::assign_slot).delete(avatars::clear_slot),
         )
+        // Avatar store routes
+        .route("/server/avatars", get(avatars::list_server_avatars))
+        .route("/realms/{slug}/avatars", get(avatars::list_realm_avatars))
+        .route(
+            "/realms/{slug}/avatar/select",
+            axum::routing::post(avatars::select_avatar),
+        )
+        .route(
+            "/realms/{slug}/avatar/selection",
+            axum::routing::delete(avatars::clear_avatar_selection),
+        )
         // User inventory routes
         .route("/user/{uuid}/inventory", get(inventory::get_user_inventory))
         .route(