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>

server.js

@@ -267,19 +267,27 @@ async function plexProxy(req, res) {
 }
 
 // ---- Storage health: is /data a real mounted volume, and what is in it? (so a wiped volume is obvious)
+/** What is mounted at the data folder? Docker's own anonymous volumes look "mounted" but are lost when the container is recreated. */
+function classifyMount(mountinfoLine) {
+  const root = (mountinfoLine || '').split(' ')[3] || '';
+  const vol = /\/volumes\/([^/]+)\/_data/.exec(root);
+  if (vol) return /^[0-9a-f]{64}$/.test(vol[1]) ? { kind: 'anonymous', name: vol[1].slice(0, 12) } : { kind: 'named', name: vol[1] };
+  return { kind: 'folder', name: root };
+}
 function storageInfo() {
   const fs = require('fs'), path = require('path');
   const dir = path.resolve(process.env.DATA_DIR || path.join(__dirname, 'data'));
-  let mounted = null; // null = cannot tell (not Linux)
-  try { mounted = fs.readFileSync('/proc/self/mountinfo', 'utf8').split('\n').some(l => l.split(' ')[4] === dir); } catch {}
+  let mounted = null, source = null; // null = cannot tell (not Linux)
+  try { const l = fs.readFileSync('/proc/self/mountinfo', 'utf8').split('\n').find(x => x.split(' ')[4] === dir); mounted = !!l; if (l) source = classifyMount(l); } catch {}
   let writable = true; try { const f = path.join(dir, '.write-test'); fs.writeFileSync(f, 'x'); fs.unlinkSync(f); } catch { writable = false; }
   const count = (f, pick) => { try { return pick(JSON.parse(fs.readFileSync(path.join(dir, f), 'utf8'))); } catch { return 0; } };
-  return { dir, mounted, writable, passkeys: count('passkeys.json', j => (j.creds || []).length), calendarLinks: count('calendars.json', j => j.length),
+  return { dir, mounted, source, writable, passkeys: count('passkeys.json', j => (j.creds || []).length), calendarLinks: count('calendars.json', j => j.length),
     events: count('events.json', j => j.length), settings: count('settings.json', j => Object.keys(j).length), icloud: fs.existsSync(path.join(dir, 'icloud.json')), secretFromEnv: !!process.env.COOKIE_SECRET,
     startedAt: STARTED };
 }
 const STARTED = Date.now();
-{ const i = storageInfo(); console.log(`[data] ${i.dir}: ${i.passkeys} passkeys, ${i.calendarLinks} calendar links, ${i.events} events; mounted volume: ${i.mounted === null ? 'unknown' : i.mounted ? 'yes' : 'NO (data is lost on redeploy)'}; writable: ${i.writable}; COOKIE_SECRET from env: ${i.secretFromEnv}`);
+{ const i = storageInfo(); console.log(`[data] ${i.dir}: ${i.passkeys} passkeys, ${i.calendarLinks} calendar links, ${i.events} events; mounted: ${i.mounted === null ? 'unknown' : i.mounted ? (i.source.kind + ' ' + i.source.name) : 'NO (data is lost on redeploy)'}; writable: ${i.writable}; COOKIE_SECRET from env: ${i.secretFromEnv}`);
+  if (i.source && i.source.kind === 'anonymous') console.warn('[data] WARNING: /data is an anonymous Docker volume, not your host folder. It is deleted when the container is recreated. Check that your stack mounts the host folder at /data.');
   if (i.mounted === false) console.warn('[data] WARNING: the data folder is not a mounted volume. Passkeys, calendars and sessions will be lost whenever the container is recreated. Mount a volume or host folder at /data.'); }
 
 if (!JWT_SECRET) console.warn('WARNING: ONLYOFFICE_JWT_SECRET not set. In-app editing only works if the Document Server has JWT disabled, and save callbacks are unauthenticated. Testing only.');