Log data location and counts at startup; give the compose volume a fixed name

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

server.js

@@ -262,6 +262,12 @@ async function plexProxy(req, res) {
   } catch (e) { if (!res.headersSent) { res.writeHead(502); res.end(); } else res.destroy(); }
 }
 
+{ // Make it obvious in the log whether data survived a redeploy.
+  const dir = process.env.DATA_DIR || require('path').join(__dirname, 'data');
+  const count = f => { try { const j = JSON.parse(require('fs').readFileSync(require('path').join(dir, f), 'utf8')); return Array.isArray(j) ? j.length : (j.creds || []).length; } catch { return 0; } };
+  console.log(`[data] ${dir}: ${count('passkeys.json')} passkeys, ${count('calendars.json')} calendars`);
+}
+
 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.');
 
 http.createServer((req, res) => {