Every new share link now carries a high-entropy passphrase (80-bit,
Crockford-base32, grouped XXXX-XXXX-XXXX-XXXX). The create response
returns the raw passphrase, the share URL, and a QR deep link EXACTLY
ONCE alongside the token; the server stores only the passphrase's HMAC
hash (the same key as the token hash). The QR deep link carries the
passphrase in the URL fragment (#k=) so it never reaches a server log,
referrer, or access record.
Add the passphrase generator, normaliser, and constant-time verifier;
the short-lived token-scoped unlock-cookie mint/verify; a gate-state
resolver that reports live + passphrase status without bumping access
counters; and the unlock request schema.