Storage panel: say what is mounted at /data and warn about Docker's anonymous volume

"mounted" was true even when /data was the hidden anonymous volume Docker creates for the
Dockerfile's VOLUME, so the app looked fine while the user's host folder stayed empty and the
data was lost when the container was recreated. Read the mount source and report host folder,
named volume or anonymous volume (flagged), in Settings and the startup log.

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

public/app.js

@@ -1088,9 +1088,13 @@ function viewSettings() {
     if (st.signedIn) { const b = $('#plexout'); b.hidden = false; b.onclick = async () => { await jfetch('/api/plex/logout', { method: 'POST' }); pl.a.pause(); pl.q = []; pl.i = -1; renderMini(); toast('Signed out of Plex'); viewSettings(); }; }
   }).catch(() => { const el = $('#plexst'); if (el) el.textContent = 'Unavailable'; });
   jfetch('/api/system').then(i => {
-    const ok = i.mounted !== false && i.writable, row = (t, d, bad) => `<div class="row"><span class="grow"><b>${t}</b><small style="white-space:normal;${bad ? 'color:var(--danger)' : ''}">${d}</small></span></div>`;
+    const anon = i.source && i.source.kind === 'anonymous', ok = i.mounted !== false && !anon && i.writable;
+    const row = (t, d, bad) => `<div class="row"><span class="grow"><b>${t}</b><small style="white-space:normal;${bad ? 'color:var(--danger)' : ''}">${d}</small></span></div>`;
+    const where = !i.source ? '' : i.source.kind === 'folder' ? ' · host folder ' + esc(i.source.name) : i.source.kind === 'named' ? ' · volume "' + esc(i.source.name) + '"' : '';
     $('#stor').innerHTML =
-      row(ok ? 'Data is saved on a volume' : 'Data is NOT being kept', i.mounted === false ? 'The data folder is not a mounted volume, so passkeys, calendars and sign-ins are lost when the container is recreated. Mount a volume or a host folder at ' + esc(i.dir) + '.' : !i.writable ? 'The data folder is not writable by the app.' : esc(i.dir) + (i.mounted ? ' (mounted)' : ''), !ok)
+      row(ok ? 'Data is saved on a volume' : 'Data is NOT being kept safely', anon ? 'This is a temporary Docker volume (' + esc(i.source.name) + '…), NOT your host folder. It is deleted when the container is recreated, and your folder stays empty. Check that your stack mounts the host folder at ' + esc(i.dir) + '.'
+        : i.mounted === false ? 'The data folder is not a mounted volume, so passkeys, calendars and sign-ins are lost when the container is recreated. Mount a volume or a host folder at ' + esc(i.dir) + '.'
+        : !i.writable ? 'The data folder is not writable by the app.' : esc(i.dir) + ' (mounted' + where + ')', !ok)
       + row('What is stored', `${i.passkeys} passkey${i.passkeys === 1 ? '' : 's'} · ${i.events} NE Hub event${i.events === 1 ? '' : 's'} · ${i.calendarLinks} calendar link${i.calendarLinks === 1 ? '' : 's'} · ${i.settings || 0} saved setting${i.settings === 1 ? '' : 's'}${i.icloud ? ' · iCloud connected' : ''}`)
       + row('Session secret', i.secretFromEnv ? 'Set in the stack (sign-ins survive restarts)' : 'Generated and kept in the data folder', false)
       + row('Running since', new Date(i.startedAt).toLocaleString(), false);