calendar: pull March's sanctoral calendar (pre-1955 pull, 3/12)

7 saints for March, all winning outright on a clean per-annum date. Notably
St. Benedict himself (Mar 21, Duplex I. classis, the founder — "S. P. N."
in the source) turns out to have no unique Oratio/Antiphon at all in this
date's source file, only Common-of-an-Abbot cross-references — flagged in
his own file to check his second (July) feast when that month comes up.

Two Benedictine-oblate saints (Frances of Rome, Gregory the Great) are
marked "O. N." (Ordinis Nostri) in the source — real significance for a
monastic calendar. St. Frances also needed a new common category,
common-of-a-widow (she's neither virgin nor martyr).

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

src/data/calendar/sanctoral-calendar.yml

@@ -56,6 +56,17 @@ days:
   "02-22": [chair-of-st-peter-at-antioch]
   "02-23": [vigil-of-st-matthias]
   "02-24": [st-matthias]
+  # March — 3/12 of the pre-1955 pull. Same exclusions as before (fixed
+  # BVM feast: Annunciation Mar 25). St. Benedict's own day (Mar 21,
+  # Duplex I. classis, the highest rank in this set so far) has no
+  # unique propers in the source at all — see st-benedict.yml.
+  "03-04": [st-lucius-i]
+  "03-07": [st-thomas-aquinas]
+  "03-09": [st-frances-of-rome]
+  "03-10": [forty-holy-martyrs]
+  "03-12": [st-gregory-the-great]
+  "03-19": [st-joseph]
+  "03-21": [st-benedict]
   "08-09": [vigil-of-st-lawrence]
   "08-10": [st-lawrence]
   "08-15": [assumption]