propers: Benedictus antiphons for April's sanctoral entries (8/8)

All 8 authored fresh: Francis of Paola, Leo I, Ss. Tiburtius/Valerian/
Maximus, George, Mark, Vitalis, Robert, Peter Martyr. Several share
one Eastertide Common-of-Several-Martyrs antiphon word for word
(Tiburtius/Valerian/Maximus, George, Vitalis, Peter Martyr) -- each
confirmed independently via its own live query rather than assumed
from the others.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/data/propers/common/st-robert-antiphon.yml

@@ -0,0 +1,9 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617), Lauds
+# live query, St. Robert's own day (2026-04-29). The Benedictus antiphon.
+id: st-robert-antiphon
+text:
+  la: "Euge, serve bone et fidélis, quia in pauca fuísti fidélis, supra multa te constítuam, intra in gáudium Dómini tui, allelúja."
+  en: "Well done, thou good and faithful servant; thou hast been faithful over a few things, I will make thee ruler over many things; enter thou into the joy of thy Lord, alleluia."
+status:
+  la: verified
+  en: verified