Bug: Username field on Feed Fidget doesn't work for Farcaster users

[willyogo]

In the settings for Feed Fidget, the username field is displayed for all Feed options, but currently only works for The Other App (X).

AC:

1. When filtering a Farcaster feed to a specific user, the FID field is removed
2. Users can input a farcaster username when filtering the Farcaster feed to a specific user
3. The username field is removed from the other Farcaster feed options (following & channel filter)