Restructure project to root layout

public/icons/icon.svg

@@ -0,0 +1,15 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 200 200" role="img" aria-label="StockFill logo">
+  <defs>
+    <linearGradient id="grad" x1="0%" y1="0%" x2="100%" y2="100%">
+      <stop offset="0%" stop-color="#0d6efd" />
+      <stop offset="100%" stop-color="#0abf9e" />
+    </linearGradient>
+  </defs>
+  <rect width="200" height="200" rx="24" fill="url(#grad)" />
+  <g fill="#ffffff">
+    <rect x="44" y="54" width="112" height="18" rx="9" opacity="0.9" />
+    <rect x="44" y="91" width="112" height="18" rx="9" opacity="0.9" />
+    <rect x="44" y="128" width="92" height="18" rx="9" opacity="0.9" />
+    <circle cx="144" cy="137" r="16" />
+  </g>
+</svg>

public/manifest.json

@@ -0,0 +1,16 @@
+{
+  "name": "StockFill",
+  "short_name": "StockFill",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#ffffff",
+  "theme_color": "#0d6efd",
+  "icons": [
+    {
+      "src": "/icons/icon.svg",
+      "sizes": "any",
+      "type": "image/svg+xml",
+      "purpose": "any"
+    }
+  ]
+}

public/service-worker.js

@@ -0,0 +1,48 @@
+const CACHE_NAME = 'stockfill-cache-v1';
+const OFFLINE_URLS = ['/', '/index.html'];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => {
+      return cache.addAll(OFFLINE_URLS);
+    }),
+  );
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(
+        keys.map((key) => {
+          if (key !== CACHE_NAME) {
+            return caches.delete(key);
+          }
+          return undefined;
+        }),
+      ),
+    ),
+  );
+});
+
+self.addEventListener('fetch', (event) => {
+  const { request } = event;
+  if (request.method !== 'GET') return;
+
+  event.respondWith(
+    fetch(request)
+      .then((response) => {
+        const copy = response.clone();
+        caches.open(CACHE_NAME).then((cache) => cache.put(request, copy));
+        return response;
+      })
+      .catch(async () => {
+        const cached = await caches.match(request);
+        if (cached) return cached;
+        if (request.mode === 'navigate') {
+          const fallback = await caches.match('/index.html');
+          if (fallback) return fallback;
+        }
+        throw new Error('Network error');
+      }),
+  );
+});