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) {