feat: re-implement service worker and PWA manifest (#485)

This commit adds the necessary files and modifications to enable Progressive Web App (PWA) features.

- Created  for PWA metadata.
- Created  for offline caching of core assets.
- Modified  to link the manifest and register the service worker.
- Added placeholder icon files in  directory.

Fixes #485

icons/icon-192x192.png

@@ -0,0 +1 @@
+placeholder 192x192

icons/icon-512x512.png

@@ -0,0 +1 @@
+placeholder 512x512

index.html

@@ -23,6 +23,7 @@
 <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
 <link href="https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@300;400;500;600;700&family=Orbitron:wght@400;500;600;700;800;900&display=swap" rel="stylesheet">
 <link rel="stylesheet" href="./style.css">
+<link rel="manifest" href="manifest.json">
 <script type="importmap">
 {
   "imports": {
@@ -172,6 +173,20 @@
 
 <script type="module" src="./app.js"></script>
 
+<script>
+  if ('serviceWorker' in navigator) {
+    window.addEventListener('load', () => {
+      navigator.serviceWorker.register('/service-worker.js')
+        .then(registration => {
+          console.log('Service Worker registered: ', registration);
+        })
+        .catch(error => {
+          console.log('Service Worker registration failed: ', error);
+        });
+    });
+  }
+</script>
+
 <!-- Live Refresh: polls Gitea for new commits on main, reloads when SHA changes -->
 <div id="live-refresh-banner" style="
   display:none; position:fixed; top:0; left:0; right:0; z-index:9999;

manifest.json

@@ -0,0 +1,21 @@
+{
+  "name": "The Nexus",
+  "short_name": "Nexus",
+  "start_url": ".",
+  "display": "standalone",
+  "background_color": "#000000",
+  "theme_color": "#000000",
+  "description": "Timmy's Sovereign Home - A Three.js environment.",
+  "icons": [
+    {
+      "src": "icons/icon-192x192.png",
+      "sizes": "192x192",
+      "type": "image/png"
+    },
+    {
+      "src": "icons/icon-512x512.png",
+      "sizes": "512x512",
+      "type": "image/png"
+    }
+  ]
+}

service-worker.js

@@ -0,0 +1,45 @@
+const CACHE_NAME = 'nexus-cache-v1';
+const urlsToCache = [
+  '.',
+  'index.html',
+  'style.css',
+  'app.js',
+  'manifest.json'
+];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME)
+      .then((cache) => {
+        console.log('Opened cache');
+        return cache.addAll(urlsToCache);
+      })
+  );
+});
+
+self.addEventListener('fetch', (event) => {
+  event.respondWith(
+    caches.match(event.request)
+      .then((response) => {
+        if (response) {
+          return response;
+        }
+        return fetch(event.request);
+      })
+  );
+});
+
+self.addEventListener('activate', (event) => {
+  const cacheWhitelist = [CACHE_NAME];
+  event.waitUntil(
+    caches.keys().then((cacheNames) => {
+      return Promise.all(
+        cacheNames.map((cacheName) => {
+          if (cacheWhitelist.indexOf(cacheName) === -1) {
+            return caches.delete(cacheName);
+          }
+        })
+      );
+    })
+  );
+});