Fix invalid HTML structure (unclosed <main>, orphan </footer>) on index, contact, shop pages (#162) (#163) (#164)

* Fix missing main/footer HTML structure in index, contact, shop pages

Agent-Logs-Url: https://github.com/DavidKRK/DavidKRK.github.io/sessions/22a9b0b3-0b65-40f6-8d32-31b6fb1f1905



* Move social icons into footer in contact.html

Agent-Logs-Url: https://github.com/DavidKRK/DavidKRK.github.io/sessions/73fb46a3-65a6-497f-90fe-72daccefd627



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Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com>

Author: DavidKRK