Telegram Bot API 8.0+ adds a `signature` field to WebApp initData.
Per the official spec, both `hash` and `signature` must be excluded
from the data-check-string before HMAC verification. Without this,
users with newer Telegram clients get a hash mismatch and 401.
Also remove redundant `unquote()` in telegram_auth.py — `parse_qsl`
already URL-decodes values, so the extra decode could corrupt user
data containing percent-like sequences.