refactor(report): consolidate 27 render helpers into render_helpers.py

feat(sprint-A6): WCAG niveau A bloquant — skip-link, canvas a11y, scope=col

refactor(arch): Sprint A3 — refactor cercles + importers (B-1, B-2, B-3, m-17)

refactor(core): faire de core/ un cercle 1 strict, déplacer cercle 2 vers measurements/

sprint72: vue HTML Worst lines globale (A.I.1 chantier 1, clôture A.I.1)