calendar: real occurrence/precedence resolution (feast ranks, sanctoral content)

Replaces the FeastRank placeholder with a real ordered FeastClass (the old
pre-1955 six-level scale) and a new TemporalCategory (privileged/ordinary
Sunday/feria). calendar/commemorations.ts's decideOccurrence encodes the
actual precedence rules as explicit, commented branches per category
rather than the reference engine's own opaque numeric weights — this app
targets one ruleset, so the readability trade-off is worth it. Category
membership (data/calendar/temporal-categories.yml) is a best-effort
reconstruction of the pre-1955 tradition, not sourced from a primary text;
expect corrections.

calendar/feasts.ts resolves real sanctoral candidates, and resolveDay()
wires it all together — occurring/temporalCategory are no longer stubs.
isDoubleOrHigher (hours/antiphon.ts) is now a real comparison instead of
a hardcoded false.

Seeded 7 real saints/feasts, each verified directly against Divinum
Officium's own rank data (not reconstructed from memory) as a small,
growable start: St. Lawrence, the Assumption, St. Augustine, the Nativity
of the BVM, St. Michael, All Saints, the Immaculate Conception.

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

@@ -0,0 +1,8 @@
+# Verified against Divinum Officium (web/www/horas/Latin/Sancti/08-10.txt,
+# untagged/default [Rank] block — the pre-1955 value, not the "(sed rubrica
+# 196)" alternate given alongside it in that file).
+id: st-lawrence
+name: "St. Lawrence, Martyr"
+rank: duplex-2-classis
+common: common-of-a-martyr
+propers: null