feat: Initial commit Plants vs Zombies Web Edition v2.4

- 5 Biomes: Day, Night, Pool, Fog, Roof (25 Campaign levels)
- Minigames: Wall-nut Bowling, I Zombie, Roguelike, Boss Rush & Dr. Zomboss
- Systems: Zen Garden, Workshop Crafting, Almanac, Tree of Wisdom, Achievements
- Backend: REST API + SQLite Accounts & Save Synchronization
- Infrastructure: Nginx HTTPS & Docker deployment

game/sw.js

@@ -0,0 +1,85 @@
+// Plants vs Zombies PWA Service Worker (Offline Support)
+const CACHE_NAME = 'pvz-web-v2.3';
+const ASSETS_TO_CACHE = [
+  './',
+  './index.html',
+  './manifest.json',
+  './favicon.ico',
+  './icon-192.png',
+  './icon-512.png',
+  './css/style.css',
+  './js/main.js',
+  './js/game.js',
+  './js/entities/plant.js',
+  './js/entities/zombie.js',
+  './js/entities/projectile.js',
+  './js/systems/grid.js',
+  './js/systems/economy.js',
+  './js/systems/combat.js',
+  './js/systems/campaign.js',
+  './js/systems/feedback.js',
+  './js/systems/wave.js',
+  './js/systems/workshop.js',
+  './js/systems/zengarden.js',
+  './js/systems/almanac.js',
+  './js/systems/achievements.js',
+  './js/systems/roguelike.js',
+  './js/systems/tree.js',
+  './js/systems/boss.js',
+  './js/systems/leaderboard.js',
+  './js/systems/auth.js',
+  './js/utils/assets.js',
+  './js/utils/test_api.js'
+];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => {
+      return cache.addAll(ASSETS_TO_CACHE);
+    }).then(() => self.skipWaiting())
+  );
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) => {
+      return Promise.all(
+        keys.filter((key) => key !== CACHE_NAME).map((key) => caches.delete(key))
+      );
+    }).then(() => self.clients.claim())
+  );
+});
+
+self.addEventListener('fetch', (event) => {
+  // Navigation or static asset request
+  if (event.request.method !== 'GET') return;
+
+  event.respondWith(
+    caches.match(event.request).then((cachedResponse) => {
+      if (cachedResponse) {
+        // Fetch in background to update cache
+        fetch(event.request).then((networkResponse) => {
+          if (networkResponse && networkResponse.status === 200) {
+            caches.open(CACHE_NAME).then((cache) => cache.put(event.request, networkResponse));
+          }
+        }).catch(() => {});
+        return cachedResponse;
+      }
+      return fetch(event.request).then((networkResponse) => {
+        if (!networkResponse || networkResponse.status !== 200 || networkResponse.type !== 'basic') {
+          return networkResponse;
+        }
+        const responseToCache = networkResponse.clone();
+        caches.open(CACHE_NAME).then((cache) => {
+          cache.put(event.request, responseToCache);
+        });
+        return networkResponse;
+      }).catch(() => {
+        // Fallback to cached index.html for navigation requests
+        if (event.request.mode === 'navigate') {
+          return caches.match('./index.html');
+        }
+      });
+    })
+  );
+});