feat: Add WFW-Aushang web app with PWA support, offline caching, and dark mode

- Created index.html for the main application interface with responsive design and dark mode support.
- Added manifest.webmanifest for PWA configuration, including app icons and display settings.
- Implemented service worker (sw.js) for offline caching of assets and network-first strategy for versioning.
- Introduced version.json to manage app versioning.

zuss/sw.js

@@ -0,0 +1,59 @@
+// Simple offline cache for kiosk usage
+const CACHE = "wfw-aushang-2025.12.24.2";
+
+const ASSETS = [
+  "/zuss/",
+  "/zuss/index.html",
+  "/zuss/app.js",
+  "/zuss/manifest.webmanifest",
+  "/zuss/version.json",
+  "/zuss/icons/icon-192.png",
+  "/zuss/icons/icon-512.png"
+];
+
+self.addEventListener("install", (event) => {
+  event.waitUntil(
+    caches.open(CACHE).then((c) => c.addAll(ASSETS)).then(() => self.skipWaiting())
+  );
+});
+
+self.addEventListener("activate", (event) => {
+  event.waitUntil(
+    (async () => {
+      const keys = await caches.keys();
+      await Promise.all(keys.map(k => (k === CACHE ? null : caches.delete(k))));
+      await self.clients.claim();
+    })()
+  );
+});
+
+// Network-first for version.json + list, cache-first for static assets
+self.addEventListener("fetch", (event) => {
+  const url = new URL(event.request.url);
+
+  // Only handle same-origin requests
+  if (url.origin !== self.location.origin) return;
+
+  const isVersion = url.pathname.endsWith("/zuss/version.json");
+
+  if (isVersion) {
+    event.respondWith(
+      fetch(event.request, { cache: "no-store" }).catch(() => caches.match(event.request))
+    );
+    return;
+  }
+
+  // Cache-first for our own static assets
+  if (url.pathname.startsWith("/zuss/")) {
+    event.respondWith(
+      caches.match(event.request).then((cached) => {
+        if (cached) return cached;
+        return fetch(event.request).then((resp) => {
+          const copy = resp.clone();
+          caches.open(CACHE).then((c) => c.put(event.request, copy));
+          return resp;
+        });
+      })
+    );
+  }
+});