Panel web: servers, capes, player profiles, auth server settings

- Servers: live status, players and TPS; add a server and get its token
  with copy-paste setup for the plugin/mod and authlib-injector; detail
  page with leaderboard (sortable), online players and activity feed
- Capes: upload, preview, and choose who can wear each one
- Players: click a player for their skin (upload, arm style, reset),
  cape, playtime and per-server stats; disable with a reason
- Settings: Microsoft section replaced by the auth server (public
  address, Yggdrasil URL, start flag, signing key)
- Dashboard: players online now and connected servers
- Avatars come from the panel's own skins

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011ARcGWxLx21FwXJ3yfGriS

panel/server/src/routes/mod.rs

@@ -45,6 +45,7 @@ pub fn api(state: &AppState) -> Router<AppState> {
         .route("/instances/{id}/files", post(admin::upload_files).delete(admin::delete_file))
         .route("/uploads", post(admin::upload_media))
         .route("/users/{id}/skin", post(admin::admin_set_skin).delete(admin::admin_delete_skin))
+        .route("/users/{id}/skin/model", axum::routing::put(admin::admin_set_model))
         .route("/users/{id}/cape", axum::routing::put(admin::admin_set_cape))
         .route("/capes", get(admin::list_capes).post(admin::create_cape))
         .route("/capes/{id}", axum::routing::put(admin::update_cape).delete(admin::delete_cape))