AI panel creation, rate limits, and UI improvements

A mix of new features, fixes, and polish in this release:

• AI panel creation — you can now create panels directly from the dashboard by answering a few questions and selecting how many questions to include. No manual setup needed.
• Minimum guild age requirement — panels can now require a minimum server age before a user can apply. This is configurable per panel from the dashboard.
• Rate limits for Discord commands — commands are now rate-limited to reduce abuse, with notifications shown on the website when a limit is hit.
• Notifications redesign — the notifications UI has been updated with a cleaner layout and now supports markdown formatting.
• Fixed an issue where application history was returning an error.
• Fixed incorrect min/max character validation on questions — setting these values is more straightforward now.
• Fixed a minor bug on the status page.