Replaces placeholder colors/type-scale with the documented Figma design
system (§1), and rebuilds login as three screens matching the doc exactly:
role selection, phone entry, and 6-box OTP verification with countdown
resend. Fixes a real bug along the way: normalizeIranianPhone stripped
Persian-digit keyboard input entirely instead of converting it (\D matches
non-ASCII digits too) -- added toLatinDigits/toPersianDigits and verified
the round-trip in isolation.
