solicitudes needs-info to modal skin (all three modes, cosmetic, no functional change)

MARS-376 S2 deferral (PM ruling 2026-07-03). Cosmetic-only: convert the ReviewRequest mode-replacement UI (approve/reject/needs_info) from inline-mode to a shadcn Dialog modal for Pluto skin parity. MUST be all-three-modes together — converting only needs_info makes it visually inconsistent with approve/reject. ZERO functional/server change (per-field checklist + autoMissing + operatorMessage already at parity in S2). Scope: src/app/(protected)/administrar/solicitudes/review-request.tsx only. Not urgent.