Make FAQs bookmarkable

[maebeale]

What is the goal of this PR and why is this important?

• Allow users to bookmark individual FAQs, just like workshops, resources, events, etc.
• FAQ appears as a filterable type in bookmark index/personal page dropdowns

How did you approach the change?

• Added has_many :bookmarks, as: :bookmarkable to the FAQ model
• Added "Faq" to BOOKMARKABLE_MODELS in Bookmark (auto-included in DROPDOWN_MODELS)
• Added FAQ joins to sort_by_title and title search scopes in Bookmark
• Rendered editable_bookmark_icon partial in the FAQ accordion view
• Added association spec to FAQ model test

UI Testing Checklist

• Bookmark icon appears next to each FAQ for authenticated users
• Clicking bookmark icon bookmarks/unbookmarks the FAQ
• FAQ appears in the type dropdown on bookmarks personal page
• FAQ appears in the type dropdown on bookmarks index page (admin)
• Bookmarked FAQs appear in personal bookmarks list
• Title search works for bookmarked FAQs
• Sort by title works for bookmarked FAQs

Anything else to add?

• Follows the exact same polymorphic bookmark pattern used by all other bookmarkable models

🤖 Generated with Claude Code