Separate AID and CSD PL offerings

[bethanyaconnor]

This PR:

• creates a new course offering called self-paced-pl-aid which mirrors its CSD sibling
• moves the latest CSD/AID self-paced PL course into that offering
• reverts the display name of self-paced-pl-csd to "Teaching CS Discoveries"
  See Slack thread for more details

I checked that this looked as expected in the following places:

• the PL catalog - a new card shows up for "Teaching AI discoveries" and the CSD PL is now called "Teaching CS Discoveries". Both cards also direct to the correct curriculum
• the version dropdown - self-paced-pl-csd-2025 is now the recommended curriculum for self-paced-pl-csd while self-paced-pl-csd-2026 is the recommended curriculum for self-paced-pl-aid
• the workshop dashboard - both "Teaching CS Discoveries" and "Teaching AI Discoveries" are listed as topics

A few notes:

• there is another course offering with the display name "Teaching AI Discoveries". This is an existing issue and a content issue, not a bug in code
• Ideally next year the PL course for AID will have the self self-paced-pl-aid-2027. I'm concerned about us remembering to change that next year and instead copying this pattern again. That said, nothing would break down if that did happen.