Add dids filter and followers/follows UI
Add optional "dids" query param to getFollows lexicon and server logic;
use inArray only when dids are provided and parse cursor via
Number(cursor). Wire frontend to pass dids and sanitize limit. Replace
followsAtom with a Set for efficient membership checks, add Followers
and Follows pages with infinite scroll, add activeTab atom, and add
SignInModal follow support. Also minor style tweak to default button
color.