Add service worker implementation and tests for PWA caching strategy

- Implemented a service worker (sw.js) that handles installation, activation, and fetch events.
- Added caching logic for public assets and a fallback for offline navigation.
- Created unit tests (sw.test.ts) to validate service worker behavior, including asset caching, navigation handling, and activation logic.
- Ensured that private API routes and third-party requests are excluded from caching.

styles/design-system.css

@@ -52,6 +52,8 @@
   position: relative;
   margin: -8px;
   min-height: 100vh;
+  min-height: 100dvh;
+  padding: env(safe-area-inset-top) env(safe-area-inset-right) env(safe-area-inset-bottom) env(safe-area-inset-left);
   color: var(--ds-ink);
   background: var(--ds-paper);
   @apply type-body;
@@ -770,6 +772,7 @@
   border-top: 1px solid var(--ds-rule);
   padding: 28px 0 40px;
   display: flex;
+  flex-wrap: wrap;
   justify-content: space-between;
   align-items: center;
   gap: 20px;