change year on footer to be dynamic

Author: SusanGithaigaN

flavors/blockstream/config.env

@@ -1,5 +1,5 @@
 export SITE_DESC='Blockstream Explorer is an open source block explorer providing detailed blockchain data across Bitcoin, Testnet, and Liquid. Supports Tor and tracking-free.'
-export SITE_FOOTER='© 2025 Blockstream Corporation Inc. All rights reserved.'
+export SITE_FOOTER="© $(date +%Y) Blockstream Corporation Inc. All rights reserved."
 export HEAD_HTML=\
 '<meta property="og:image" content="https://blockstream.info/img/social-sharing.png">'\
 '<meta name="twitter:image" content="https://blockstream.info/img/social-sharing.png">'\