Add buildDatabaseUrl and a CLI helper to print it

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/db.js

@@ -2,6 +2,11 @@ import mariadb from 'mariadb';
 
 let pool;
 
+export function buildDatabaseUrl(config) {
+  const { host, user, password, database } = config.db;
+  return `mysql://${encodeURIComponent(user)}:${encodeURIComponent(password)}@${host}:3306/${database}?connection_limit=10`;
+}
+
 export function getPool(config) {
   if (!pool) {
     pool = mariadb.createPool({