新增 PWA 更新提示並整理 README

public/manifest.webmanifest

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+{
+  "name": "羽球記分板",
+  "short_name": "羽球記分板",
+  "description": "羽毛球記分板，可在手機主畫面像 App 一樣開啟。",
+  "start_url": "/",
+  "scope": "/",
+  "display": "standalone",
+  "background_color": "#f4ecd8",
+  "theme_color": "#143f49",
+  "lang": "zh-Hant",
+  "orientation": "portrait",
+  "icons": [
+    {
+      "src": "/pwa-192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any maskable"
+    },
+    {
+      "src": "/pwa-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any maskable"
+    }
+  ]
+}

public/sw.js

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+const CACHE_NAME = 'badminton-scoreboard-v1'
+const APP_SHELL = [
+  '/',
+  '/index.html',
+  '/manifest.webmanifest',
+  '/favicon.svg',
+  '/apple-touch-icon.png',
+  '/pwa-192.png',
+  '/pwa-512.png',
+]
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => cache.addAll(APP_SHELL)),
+  )
+  self.skipWaiting()
+})
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(
+        keys.map((key) => {
+          if (key !== CACHE_NAME) {
+            return caches.delete(key)
+          }
+
+          return Promise.resolve(false)
+        }),
+      ),
+    ),
+  )
+  self.clients.claim()
+})
+
+self.addEventListener('message', (event) => {
+  if (event.data?.type === 'SKIP_WAITING') {
+    self.skipWaiting()
+  }
+})
+
+self.addEventListener('fetch', (event) => {
+  if (event.request.method !== 'GET') {
+    return
+  }
+
+  const requestUrl = new URL(event.request.url)
+
+  if (requestUrl.origin !== self.location.origin) {
+    return
+  }
+
+  event.respondWith(
+    caches.match(event.request).then(async (cachedResponse) => {
+      if (cachedResponse) {
+        return cachedResponse
+      }
+
+      try {
+        const networkResponse = await fetch(event.request)
+
+        if (
+          networkResponse.ok &&
+          (event.request.destination === 'document' ||
+            event.request.destination === 'script' ||
+            event.request.destination === 'style' ||
+            event.request.destination === 'image' ||
+            requestUrl.pathname.startsWith('/assets/'))
+        ) {
+          const cache = await caches.open(CACHE_NAME)
+          cache.put(event.request, networkResponse.clone())
+        }
+
+        return networkResponse
+      } catch (error) {
+        if (event.request.mode === 'navigate') {
+          const fallback = await caches.match('/index.html')
+          if (fallback) {
+            return fallback
+          }
+        }
+
+        throw error
+      }
+    }),
+  )
+})