calendar: enable the four remaining real octaves

Assumption (Aug 15-22), Nativity of the BVM (Sep 8-15), Immaculate
Conception (Dec 8-15), and All Saints (Nov 1-8) now declare octave:
{ enabled: true }, same generic mechanism as St. Lawrence and the
Christmas trio. Every octave this pull has identified is now modeled;
Matins reading content is a separate, larger follow-up (see conversation)
-- these still just commemorate at L/V-equivalent level for now.

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

src/data/calendar/saints/immaculate-conception.yml

@@ -7,3 +7,6 @@ name: "The Immaculate Conception of the Blessed Virgin Mary"
 rank: duplex-1-classis
 common: common-of-the-bvm
 propers: "immaculate-conception"
+# Has a real octave (Dec 8-15) -- see calendar/types.ts's OctaveConfig.
+octave:
+  enabled: true