feat(dashboard): add RH detail modals matching Finanzas pattern
Backend: extend /api/dashboard/consolidado with rh_headcount_detalle, rh_headcount_tendencia, rh_nomina_detalle, rh_nomina_tendencia arrays plus rotacion_pct, nuevos_mes, bajas_mes scalars. Graceful degradation if RH tables are empty.
Frontend: add ModalRhHeadcountDetalle (activos/nuevos/bajas by empresa with trend chart) and ModalRhNominaDetalle (masa salarial/ beneficios by empresa with area chart). Both have KPI strips, filter bar, and detail tables matching the Finanzas modals exactly.
Update RH consolidated card with Headcount and Nomina sub-panels featuring "Detalle" buttons, mirroring the Panel Financiero layout.
Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com