fix: logger.js hardcoded server.log path breaks non-root container user

server/utils/logger.js was still writing to ../../server.log relative
to __dirname (/app/server.log) which is root-owned. The non-root node
user (UID 1000) cannot write there, causing an EACCES crash on startup.

Fix: use DATA_DIR env var (same as index.js) so all log writes go to
/app/data/server.log which is owned by the node user.

server/utils/logger.js

@@ -1,7 +1,12 @@
 const fs = require('fs');
 const path = require('path');
 
-const logFile = fs.createWriteStream(path.join(__dirname, '../../server.log'), { flags: 'a' });
+// Use DATA_DIR so the non-root container user (UID 1000) can write logs.
+// Falls back to ../../data/server.log (same directory index.js uses).
+const DATA_DIR = process.env.DATA_DIR || path.join(__dirname, '../../data');
+if (!fs.existsSync(DATA_DIR)) fs.mkdirSync(DATA_DIR, { recursive: true });
+
+const logFile = fs.createWriteStream(path.join(DATA_DIR, 'server.log'), { flags: 'a' });
 
 function logToFile(message) {
   logFile.write(`[${new Date().toISOString()}] ${message}\n`);