vPracticaHistorial planning-cost fix for get_practica_detail_bundle, split from MARS-752

Split off MARS-752 at close (2026-10-10, SHA 08e9c80): MARS-752's crash-symptom (query cancel crashing the page) is fixed via loadOrDegrade() across /mi-cursada, /mi-cursada/[id], /practicas/[id]. NOT fixed: get_practica_detail_bundle's own fixed per-call planning cost on vPracticaHistorial (the 09-20 root theory) and the platform-stall tail latency itself (MARS-698/769 family, Elazar's dashboard-read decision from 09-20 still outstanding - see MARS-743). Reopen only if recurrence under loadOrDegrade's graceful-degrade shows the underlying query still routinely near the 10s cap.