calendar: pull July's sanctoral calendar (pre-1955 pull, 7/12)

23 saints for July (18 real + 5 stubs). Caught and corrected a real
mistake in this pull's own methodology: an earlier live-query pass
recorded St. Apollinaris under July 24 based on a year where he'd
actually transferred there (his true date, the 23rd, was a Sunday that
year) — cross-checking against the raw calendar text file
(1570.txt) caught it before it went in. His real date is the 23rd, with
St. Liborius as his (permanently unwinnable) secondary; July 24 is
instead the Vigil of St. James with St. Christina as its own secondary.

Five stubs this month are all genuinely unwinnable (fixed-date
competitors) — the most of any month so far.

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

src/data/calendar/saints/st-margaret-of-antioch.yml

@@ -0,0 +1,8 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617), live kalendar
+# check (2028-07-20, no Sunday collision) -- winner outright, Simplex. Own
+# proper collect, no unique antiphon of her own.
+id: st-margaret-of-antioch
+name: "St. Margaret of Antioch, Virgin and Martyr"
+rank: simplex
+common: common-of-a-virgin-martyr
+propers: "st-margaret-of-antioch"