Práctica notification email subject collides across recipients (Gmail collapses duplicate tag); add per-recipient discriminator

Práctica notification emails (aprobada/etc, from soporte-evolutiva-mars) use an identical subject 'tag' across recipients — e.g. 'Endodoncia / Mars / Práctica aprobada - 260623-01' went to both Maxima Konis (HC 32843342) and Julieta Bordon (HC 692899). Gmail threads/collapses identical subjects so distinct students' notifications look duplicated in the mailbox (esp Elazar's Sent, which holds every send via his creds). Fix: add a per-recipient discriminator to the práctica email subject so subjects are unique per email. FIRST confirm whether práctica number 260623-01 shared by 2 students is a legit reciprocal práctica (mutual pick, one code by design — see reciprocal-practica-duplicate memory) vs a genuine number-collision data bug; fix the subject regardless, flag if it is a data bug. Investigate subject-construction in the práctica notification mailer; pick cleanest discriminator (student name / HC / práctica-row id) per commons no-raw-UUID-in-user-facing-text rule. Reversible string change.