Create conference timeline and milestones 🎯

[laisbsc]

Establish key dates and deadlines for the conference.

• Conference date: 5 - 7 December 2025
• Send one email to previous attendees.
• Call for Proposals: July 11th - ??
• Proposals review
• Announce approved talks
• Publish conference schedule
• Conference registration opens (Pretix)
• Discord server setup
• what else?