calendar: pull February's sanctoral calendar (pre-1955 pull, 2/12)

13 saints for February (12 real + the Vigil of St. Matthias), all
verified winning outright on a clean per-annum date — no secondary/
commemorated stubs needed this month, unlike January.

Two new scope exclusions found this month, beyond the usual octave/
temporal-continuation and fixed Lord/BVM feast ones: the generic
"Sanctae Mariae Sabbato" Saturday votive (not a real saint) and Feb 29's
leap-year redirect of the Vigil of St. Matthias (a real but not-yet-
modeled leap-day date shift).

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

src/data/calendar/saints/st-valentine.yml

@@ -0,0 +1,11 @@
+# Verified against Divinum Officium (Monastic Tridentinum 1617), live kalendar
+# check (2030-02-14, a year Ash Wednesday falls in March, clear of this date,
+# and Feb 14 isn't a Sunday) -- winner outright, Simplex. In most years his
+# feast is instead overshadowed by the movable Ash Wednesday/nearby Sundays,
+# same transfer/precedence machinery as everywhere else, not re-verified
+# here. Own proper collect, no unique antiphon of his own.
+id: st-valentine
+name: "St. Valentine, Priest and Martyr"
+rank: simplex
+common: common-of-a-martyr
+propers: "st-valentine"