feat: Set up PWA infrastructure with service worker, offline support, and manifest

- Created service worker (public/sw.js) with caching strategies
  - Cache-first strategy for static assets
  - Stale-while-revalidate for API responses and pages
  - Network-first fallback strategy
- Implemented offline fallback page (/offline)
- Updated manifest.json with complete PWA metadata
- Added service worker registration in app layout
- Created ServiceWorkerRegistration component for client-side registration
- Generated SVG icons for PWA (192x192 and 512x512)
- Added PWA meta tags for iOS Safari support

Validates Requirements: 4.1, 4.3, 4.4

components/ServiceWorkerRegistration.tsx

@@ -0,0 +1,44 @@
+'use client';
+
+import { useEffect } from 'react';
+
+export default function ServiceWorkerRegistration() {
+  useEffect(() => {
+    if ('serviceWorker' in navigator) {
+      // Register service worker
+      navigator.serviceWorker
+        .register('/sw.js')
+        .then((registration) => {
+          console.log('Service Worker registered with scope:', registration.scope);
+
+          // Check for updates periodically
+          setInterval(() => {
+            registration.update();
+          }, 60000); // Check every minute
+
+          // Listen for updates
+          registration.addEventListener('updatefound', () => {
+            const newWorker = registration.installing;
+            if (newWorker) {
+              newWorker.addEventListener('statechange', () => {
+                if (newWorker.state === 'installed' && navigator.serviceWorker.controller) {
+                  // New service worker available, could show update notification
+                  console.log('New service worker available');
+                }
+              });
+            }
+          });
+        })
+        .catch((error) => {
+          console.error('Service Worker registration failed:', error);
+        });
+
+      // Listen for controller change (new service worker activated)
+      navigator.serviceWorker.addEventListener('controllerchange', () => {
+        console.log('Service Worker controller changed');
+      });
+    }
+  }, []);
+
+  return null; // This component doesn't render anything
+}