feat: cache-control overhaul so visual changes propagate immediately

Per-file content-hash versioning on every /static reference, immutable cache
headers on versioned URLs, no-cache on HTML, auto-bumped service worker cache
name with stale-while-revalidate for assets, and a controllerchange listener
that silently reloads the page when a new SW takes control.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/static/script.js

@@ -417,5 +417,11 @@ window.addEventListener('load', () => {
         navigator.serviceWorker.register('/sw.js').catch(err => {
             console.warn('Service worker registration failed:', err);
         });
+        let reloading = false;
+        navigator.serviceWorker.addEventListener('controllerchange', () => {
+            if (reloading) return;
+            reloading = true;
+            location.reload();
+        });
     }
 });

app/static/sw.js

@@ -1,63 +0,0 @@
-const CACHE = 'nhl-scoreboard-v3';
-const PRECACHE = [
-    '/',
-    '/static/styles.css',
-    '/static/script.js',
-    '/static/icon-192x192.png',
-    '/static/icon-512x512.png',
-    '/manifest.json',
-];
-
-self.addEventListener('install', event => {
-    event.waitUntil(caches.open(CACHE).then(c => c.addAll(PRECACHE)));
-    self.skipWaiting();
-});
-
-self.addEventListener('activate', event => {
-    event.waitUntil(
-        caches.keys().then(keys =>
-            Promise.all(keys.filter(k => k !== CACHE).map(k => caches.delete(k)))
-        )
-    );
-    self.clients.claim();
-});
-
-self.addEventListener('fetch', event => {
-    const { pathname } = new URL(event.request.url);
-
-    // Network-first for the live scoreboard API — stale data is useless
-    if (pathname === '/scoreboard') {
-        event.respondWith(
-            fetch(event.request).catch(() => caches.match(event.request))
-        );
-        return;
-    }
-
-    // Network-first for bracket + series detail pages; fall back to cache offline
-    if (pathname === '/bracket' || pathname.startsWith('/series/')) {
-        event.respondWith(
-            fetch(event.request).then(response => {
-                if (response.ok) {
-                    const clone = response.clone();
-                    caches.open(CACHE).then(c => c.put(event.request, clone));
-                }
-                return response;
-            }).catch(() => caches.match(event.request))
-        );
-        return;
-    }
-
-    // Cache-first for everything else (static assets, shell)
-    event.respondWith(
-        caches.match(event.request).then(cached => {
-            if (cached) return cached;
-            return fetch(event.request).then(response => {
-                if (response.ok) {
-                    const clone = response.clone();
-                    caches.open(CACHE).then(c => c.put(event.request, clone));
-                }
-                return response;
-            });
-        })
-    );
-});