server/server.js — added helmet with CSP configured to allow Google Fonts

Dockerfile — creates a non-root app user and runs the process under it
server/routes.js — tailscale_ip validated against IPv4 regex (empty string still allowed)
index.html — sql.js CDN script tag already removed earlier in this session

index.html

@@ -176,7 +176,6 @@
   <span id="toast-msg"></span>
 </div>
 
-<script src="https://cdnjs.cloudflare.com/ajax/libs/sql.js/1.10.2/sql-wasm.js"></script>
 <script src="js/version.js" onerror="window.VERSION=null"></script>
 <script src="js/config.js"></script>
 <script src="js/db.js"></script>