Add example flutter app for showcasing extension use (with hive)

Translate the main Hive x Flutter example into CLJD, to provide a working example.
https://docs.hivedb.dev/#/basics/hive_in_flutter

(ns flutter-lab.main
  "ValueListenable example from hive documentation for Flutter: https://docs.hivedb.dev/#/basics/hive_in_flutter"
  (:require ["package:flutter/material.dart" :as m]
            ["package:hive/hive.dart" :as hive]
            ["package:hive_flutter/hive_flutter.dart" :as hive-flutter]
            [cljd.flutter :as f]))


(defn main []
  (-> hive-flutter/Hive hive-flutter/HiveX .initFlutter await)
  (-> hive/Hive (.openBox "pandorra"))

  (f/run
   (m/MaterialApp
    .title "Welcome to Flutter"
    .theme (m/ThemeData .primarySwatch m.Colors/pink))
   .home
   (m/Scaffold
    .appBar (m/AppBar
             .title (m/Text "Welcome to ClojureDart")))
   .body
   (#/(m/ValueListenableBuilder hive/Box)
    ;; something something breaks here
    .valueListenable (-> (.box hive/Hive "pandorra")
                         hive-flutter/Hive
                         .listenable)
    .builder
    (fn [ctx box widget]
      (m/Center
       .child
       (m/Switch
        .value (-> box (.get "darkMode" .defaultValue false))
        .onChanged (fn [v] (-> box (.put "darkMode" v)))))))))

Start with the linked Hive Flutter documentation and the provided ClojureDart snippet, then inspect the existing example-app structure and how ClojureDart handles Flutter interop. Resolve the marked ValueListenableBuilder issue and add a working Hive-backed Flutter example that demonstrates the documented behavior.