Like a Challenge

This is a new feature for any logged-in user to "like" a challenge. This would be represented by a "thumbs up" icon like this one . Color, yellow.

The like icon would appear on the Challenge browse page to the left of the flag icon (#1868)

UI Flow

1. User clicks the "like" button
2. A cute animation confirms the like action
3. The like counter increments and the icon changes to a filled thumbs-up icon.
4. If the user already liked the challenge, clicking the icon will remove the like and the counter decrements instead, and the icon reverts to its outline state.

Conditions

1. Number of likes is displayed next to the
2. Challenge owners can not like their own challenges
3. A user must have completed at least one task of the Challenge to be able to Like it
4. Challenges that are liked more will be sorted higher in the default sort in Find Challenges
5. There will be a new sort option to sort by number of likes.

Start by locating the Challenge browse page and the Find Challenges sorting entry points in the frontend. Trace how logged-in users, challenge ownership, task completion, and challenge ordering are represented before assessing the like state and counter flow. Done should cover liking and unliking, the stated eligibility rules, visual confirmation, and both like-based sorting behaviors.