feat: onboarding wizard, PWA support, Oracle Cloud free tier deploy, mode nav update

public/sw.js

@@ -0,0 +1,40 @@
+const CACHE_NAME = 'stackpilot-v1';
+const STATIC_ASSETS = ['/', '/index.html'];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => cache.addAll(STATIC_ASSETS))
+  );
+  self.skipWaiting();
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(keys.filter((k) => k !== CACHE_NAME).map((k) => caches.delete(k)))
+    )
+  );
+  self.clients.claim();
+});
+
+self.addEventListener('fetch', (event) => {
+  const { request } = event;
+  // Don't cache API calls
+  if (request.url.includes('/api/')) {
+    event.respondWith(fetch(request));
+    return;
+  }
+  // Cache-first for static assets
+  event.respondWith(
+    caches.match(request).then((cached) => {
+      const fetched = fetch(request).then((response) => {
+        if (response.ok) {
+          const clone = response.clone();
+          caches.open(CACHE_NAME).then((cache) => cache.put(request, clone));
+        }
+        return response;
+      }).catch(() => cached);
+      return cached || fetched;
+    })
+  );
+});