1-- Device-pairing link codes: the signed-in browser mints a short-lived,2-- single-use code; the device (key-holder) redeems it to merge its account3-- into the code's user. Only the sha-256 of the code is stored.4CREATE TABLE link_codes (5 code_hash TEXT PRIMARY KEY,6 user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,7 created_at INTEGER NOT NULL,8 expires_at INTEGER NOT NULL9);10CREATE INDEX idx_link_codes_user ON link_codes(user_id);