Feature: Embed Pretalx for Live Schedule

[zorexsalvo]

This pull request updates the schedule page to embed a live, interactive event schedule using the Pretalx widget, replacing the placeholder "TO BE ANNOUNCED" message. It also introduces custom styling and improved responsiveness for mobile devices.

Schedule integration and UI improvements:

• Embedded the Pretalx schedule widget by including its external JavaScript and adding the <pretalx-schedule> element, enabling a dynamic, real-time event schedule display.
• Added custom CSS to force a light theme, override default colors, and ensure the widget matches the site's branding.
• Improved mobile responsiveness by adjusting font sizes for smaller screens within the schedule widget.

Accessibility and user messaging:

• Added a note above the schedule informing users that the schedule is subject to change, encouraging them to check back for updates.
• Included a <noscript> fallback message for users with JavaScript disabled, providing a link to a non-JavaScript version of the schedule.