-- SQLite cannot drop a NOT NULL constraint via ALTER, so rebuild the users
-- table: email becomes nullable, phone is added as a unique second identifier,
-- and existing rows are carried across (phone stays NULL).
CREATE TABLE users_new (
    id            TEXT PRIMARY KEY,
    email         TEXT UNIQUE,
    phone         TEXT UNIQUE,
    password_hash TEXT NOT NULL,
    name          TEXT NOT NULL,
    avatar_url    TEXT,
    preferences   TEXT NOT NULL DEFAULT '{}',
    created_at    TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now'))
);

INSERT INTO users_new (id, email, phone, password_hash, name, avatar_url, preferences, created_at)
SELECT id, email, NULL, password_hash, name, avatar_url, preferences, created_at FROM users;

DROP TABLE users;

ALTER TABLE users_new RENAME TO users;