Stability: cache-control at origin + non-hanging startup

Intermittent blank screens / long "Gathering the good news…" — two fixes:

Origin cache headers (Caddyfile, deployed separately): content-hashed
/_app/immutable/* → max-age=31536000, immutable; everything else (HTML shell,
service worker, version manifest, webmanifest, word lists, icons) → no-cache,
so a deploy can't leave a stale shell/SW pinned. (Cloudflare's 4h Browser Cache
TTL still overrides this until its dashboard setting is switched to "Respect
Existing Headers" — that's the actual root cause.)

App startup hardening:
* getJSON now has a 10s AbortController timeout — a stuck request can never hang
  the loading state forever.
* Home onMount loads moods+categories in parallel then the view, with loading
  ALWAYS cleared in finally; lanes/families dropped to non-blocking decoration.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/lib/api.js

@@ -1,7 +1,13 @@
-export async function getJSON(url) {
-  const r = await fetch(url);
-  if (!r.ok) throw new Error((await r.text().catch(() => '')) || r.statusText);
-  return r.json();
+export async function getJSON(url, { timeout = 10000 } = {}) {
+  const ctrl = new AbortController();
+  const t = setTimeout(() => ctrl.abort(), timeout);   // never hang on a stuck request
+  try {
+    const r = await fetch(url, { signal: ctrl.signal });
+    if (!r.ok) throw new Error((await r.text().catch(() => '')) || r.statusText);
+    return await r.json();
+  } finally {
+    clearTimeout(t);
+  }
 }
 
 export async function postJSON(url, body) {

frontend/src/routes/+page.svelte

@@ -429,19 +429,29 @@
     dismissed = new Set(P.loadJSON(DISMISSED_KEY, []));
     refreshAuth();
     trackVisit();
+    // Critical path: moods + categories (needed to resolve a mood/topic view)
+    // load in PARALLEL, then the requested view. Every getJSON times out, and
+    // loading ALWAYS clears in finally, so the page can never get stuck on
+    // "Gathering the good news…".
     try {
-      moods = await getJSON('/api/moods');
-      topics = (await getJSON('/api/categories')).topics;
-      try { lanePool = await getJSON('/api/lanes'); } catch { lanePool = null; }
-      try { families = await getJSON('/api/families'); } catch { families = []; }
-      // Load whatever the URL asks for (Highlights, or a deep-linked source/tag/
-      // view) — the param stays in the URL so reload and share are honest.
+      const [m, c] = await Promise.all([
+        getJSON('/api/moods').catch(() => []),
+        getJSON('/api/categories').catch(() => ({ topics: [] })),
+      ]);
+      moods = m; topics = c.topics;
       await loadView(selected);
     } catch (e) {
       error = 'Could not reach Upbeat Bytes.';
+    } finally {
+      loading = false;
     }
-    loading = false;
     checkSince(); // after the first paint; non-blocking
+    // Pure decoration (nav-rail customization + tag families): non-blocking — a
+    // slow or failed one fills in late instead of holding up the content.
+    Promise.allSettled([
+      getJSON('/api/lanes').then((r) => (lanePool = r)),
+      getJSON('/api/families').then((r) => (families = r)),
+    ]);
   });
 </script>