Always revalidate the app's files, tell open pages when a newer version exists, and log why a session is refused

An open page kept running the old version after a deploy (the single page never reloads), so the new
People screens did not appear. Static files are now sent with no-cache + ETag (304 when unchanged), icons
are cached for a week, /api/config reports a build stamp, and the app shows "A new version is available -
Reload" when it comes back into view or every 10 minutes. The service worker cache name is bumped.

The server also logs, at most once a minute per reason, why it refused a session cookie (unknown account,
turned off, signed out everywhere, bad signature, expired) without printing the cookie.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/style.css

@@ -246,3 +246,9 @@ html { -webkit-text-size-adjust: 100%; overscroll-behavior: none; }
 body { -webkit-touch-callout: none; }
 button, a, .row { -webkit-user-select: none; user-select: none; }
 input, textarea, [contenteditable], .sheet p, .card p, #view .sub { -webkit-user-select: text; user-select: text; }
+
+/* "A new version is available" notice */
+#upd { position: fixed; left: 50%; transform: translateX(-50%); bottom: calc(var(--nav-h) + var(--sab) + 70px); z-index: 30; display: flex; align-items: center; gap: 12px;
+  background: var(--text); color: var(--bg); padding: 8px 8px 8px 16px; border-radius: 14px; box-shadow: 0 6px 24px rgba(0,0,0,.35); max-width: 92vw; }
+#upd .btn { min-height: 36px; background: var(--accent); color: var(--accent-t); }
+@media (min-width: 768px) { #upd { bottom: 24px; } }