fix(offline): fall back to cached shell on upstream 5xx

Service worker previously only fell back to cache when fetch threw
(network unreachable). A 502/503/504 from the origin returned
successfully with !response.ok, so the bad page was passed through to
the user. Now upstream 5xx is treated like a network failure: try
cached page, then offline-shell redirect for recipe routes, then the
styled offline page. 4xx still passes through unchanged.

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "homepage",
-	"version": "1.67.3",
+	"version": "1.67.4",
 	"private": true,
 	"type": "module",
 	"scripts": {

src/service-worker.ts

@@ -117,30 +117,34 @@ sw.addEventListener('fetch', (event) => {
 				// SvelteKit adds ?x-sveltekit-invalidated=... which we need to ignore
 				const cacheKey = url.pathname;
 
+				let response: Response | undefined;
 				try {
-					// Try network first
-					const response = await fetch(event.request);
+					response = await fetch(event.request);
+				} catch {
+					// Network unreachable — fall through to cache fallback below.
+				}
 
 				// Cache successful responses for offline use (using pathname as key)
-					if (response.ok) {
+				if (response?.ok) {
 					cache.put(cacheKey, response.clone());
-					}
-
 					return response;
-				} catch {
-					// Network failed - try to serve from cache (ignoring query params)
-					const cached = await cache.match(cacheKey);
-					if (cached) {
-						return cached;
 				}
 
-					// No cached data available - return error response
-					// The page will need to handle this gracefully
+				// Network unreachable OR upstream 5xx (502/503/504 etc.) — serve
+				// stale cached data so the PWA stays usable when the origin is down.
+				if (!response || response.status >= 500) {
+					const cached = await cache.match(cacheKey);
+					if (cached) return cached;
+				}
+
+				// Pass through non-5xx errors (404, 401, ...) untouched.
+				if (response) return response;
+
+				// No response and no cache — synthetic offline error.
 				return new Response(JSON.stringify({ error: 'offline' }), {
 					status: 503,
 					headers: { 'Content-Type': 'application/json' }
 				});
-				}
 			})()
 		);
 		return;
@@ -222,27 +226,32 @@ sw.addEventListener('fetch', (event) => {
 				// Use pathname only for cache key (ignore query params)
 				const cacheKey = url.pathname;
 
+				let response: Response | undefined;
 				try {
-					// Try network first
-					const response = await fetch(event.request);
+					response = await fetch(event.request);
+				} catch {
+					// Network unreachable — fall through to fallback below.
+				}
 
 				// Cache successful HTML responses for cacheable pages (using pathname as key)
-					const isCacheablePage = response.ok && (
+				if (response?.ok) {
+					const isCacheablePage =
 						url.pathname.match(/^\/(rezepte|recipes|glaube|faith|fitness)(\/|$)/) ||
-						url.pathname === '/'
-					);
+						url.pathname === '/';
 					if (isCacheablePage) {
 						cache.put(cacheKey, response.clone());
 					}
-
 					return response;
-				} catch {
-					// Network failed - try to serve from cache (ignoring query params)
-					const cached = await cache.match(cacheKey);
-					if (cached) {
-						return cached;
 				}
 
+				// Network unreachable OR upstream 5xx (502 Bad Gateway, 503, 504, ...) —
+				// serve stale shell so the PWA stays usable when the origin is down.
+				const upstreamDown = !response || response.status >= 500;
+
+				if (upstreamDown) {
+					const cached = await cache.match(cacheKey);
+					if (cached) return cached;
+
 					// For recipe routes, redirect to the offline shell with the target URL
 					// The offline shell will then do client-side navigation to load from IndexedDB
 					// Skip if this is already the offline-shell or an offline navigation to prevent loops
@@ -262,6 +271,10 @@ sw.addEventListener('fetch', (event) => {
 							return Response.redirect(redirectUrl, 302);
 						}
 					}
+				}
+
+				// Pass through non-5xx errors (404, 401, ...) untouched.
+				if (response && !upstreamDown) return response;
 
 				// Last resort - return a styled offline response
 				return new Response(
@@ -299,7 +312,6 @@ p{color:#aaa}
 </body></html>`,
 					{ headers: { 'Content-Type': 'text/html' } }
 				);
-				}
 			})()
 		);
 		return;