feat: add PWA support with offline caching

- Generate 192x192, 512x512 and Apple touch icons from favicon.svg
- Add web app manifest (manifest.json)
- Add service worker with network-first for HTML, cache-first for assets
- Register SW in BaseLayout
- Add theme-color meta and apple-touch-icon link

public/manifest.json

@@ -0,0 +1,24 @@
+{
+  "name": "Randify — Random Value Generators",
+  "short_name": "Randify",
+  "description": "Simple tools for raffles, games, and everything that needs randomness.",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#09090b",
+  "theme_color": "#534AB7",
+  "orientation": "portrait-primary",
+  "scope": "/",
+  "lang": "en",
+  "icons": [
+    {
+      "src": "/icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png"
+    },
+    {
+      "src": "/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png"
+    }
+  ]
+}