Allow users to configure their privacy settings

Users should be able to configure what parts of their profile are visible to the public. Currently all users' first and last names are visible in the project gallery, but they should be able to choose to be anonymous, or perhaps also show some contact info.

Once #31 is complete and the Privacy tab exists under the account dashboard, we should add a section to configure which details of a user are public. Initially it could be the following:

- First name (on by default)
- Last name (on by default)
- Email (off by default)

Start by reviewing issue #31 and the account dashboard work that introduces the Privacy tab; no files or tests are named here. Trace how profile details are displayed in the project gallery and identify where the three proposed visibility choices belong. Done means users can configure first name, last name, and email visibility with the stated defaults, and the gallery respects those choices.

索引モデルが issue の本文から書いたものです。