-- Profile bio — a short self-introduction shown on the profile header.
--
-- Plain text (never HTML): `@handle` mentions are stored verbatim and linkified
-- at render time by the frontend, so nothing user-supplied is ever trusted as
-- markup. NULL means "no bio set", which is distinct from an empty string —
-- the update path clears to NULL rather than storing ''.
--
-- The 200-character cap is enforced in the service layer (by rune count, so a
-- devotee writing in Devanāgarī gets the same 200 characters a Latin-script
-- writer does). No CHECK constraint here: the column stays permissive so a
-- future cap change doesn't need a migration on a large table.
ALTER TABLE users
    ADD COLUMN IF NOT EXISTS bio TEXT;