Elevate planner UX and offline resilience

public/sw.js

@@ -1,7 +1,8 @@
-const CACHE_NAME = "roast-planner-static-v3";
+const CACHE_NAME = "roast-planner-static-v4";
 const APP_SHELL = [
 	"/",
 	"/landing.html",
+	"/app",
 	"/app.css",
 	"/worksheet.css",
 	"/manifest.webmanifest",
@@ -23,7 +24,6 @@ self.addEventListener("install", (event) => {
 	event.waitUntil(
 		caches.open(CACHE_NAME).then((cache) => cache.addAll(APP_SHELL)),
 	);
-	self.skipWaiting();
 });
 
 self.addEventListener("activate", (event) => {
@@ -57,10 +57,12 @@ self.addEventListener("fetch", (event) => {
 		return;
 
 	if (request.mode === "navigate") {
-		// Never serve authenticated application HTML from cache after logout.
-		event.respondWith(
-			fetch(request).catch(() => caches.match("/landing.html")),
-		);
+		// /app is a data-free authenticated shell: draft data lives only in account-scoped
+		// local storage and logout clears that namespace. This makes offline relaunch useful
+		// without ever caching account data or API responses.
+		event.respondWith(fetch(request).catch(() =>
+			url.pathname === "/app" ? caches.match("/app") : caches.match("/landing.html"),
+		));
 		return;
 	}
 
@@ -78,3 +80,7 @@ self.addEventListener("fetch", (event) => {
 			.catch(() => caches.match(request)),
 	);
 });
+
+self.addEventListener("message", (event) => {
+	if (event.data === "SKIP_WAITING") self.skipWaiting();
+});