-- 0003 — Phase 3 (PWA POS).
-- pin_pbkdf2: PBKDF2-SHA256 PIN hash the PWA verifies offline via WebCrypto (D18).
-- variance columns: per-branch shift variance tolerance (doc 06 §3, D22) —
-- tolerance should never be zero; cash rounding alone produces small differences.

ALTER TABLE users ADD COLUMN pin_pbkdf2 VARCHAR(255) NULL;

ALTER TABLE branches ADD COLUMN variance_tolerance_iqd INT NOT NULL DEFAULT 1000;
ALTER TABLE branches ADD COLUMN variance_hard_threshold_iqd INT NOT NULL DEFAULT 10000;
