Relocate Immaculate Heart of Mary off Aug 22 to Easter+69

Fixed Aug 22 collided outright with the Assumption's own octave-closing
day (both this project's blended calendar tracks are kept deliberately,
so one shouldn't permanently suppress the other). Moved IHM to the
Saturday after the Feast of the Sacred Heart -- its real diocesan date
from 1914 until Pius XII's 1944 fixed-date decree, and also the date the
1969 reform returned to.

Required real new mechanism, not just a data move: a new bespoke
calendar/index.ts override (applyImmaculateHeart, following the existing
applyMarianSaturday/applyChristTheKing precedent), a move from the
sanctoral saints store to the temporal-feasts store (different propers
lookup entirely), and a real bug fix in matins.ts's nocturnReadingIds,
which only ever picked up a *sanctoral* winner's own reading file.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VZSAgRi4QE4XRTqVto93zA

src/data/propers/common/immaculate-heart-of-mary-antiphon.yml

@@ -1,10 +0,0 @@
-# Read directly from web/www/horas/Latin/Sancti/08-22.txt's own
-# [Ant 1] and its English counterpart -- a real, proper antiphon of
-# this feast, not a Common substitution.
-id: immaculate-heart-of-mary-antiphon
-text:
-  la: "Exsultávit cor meum * in Dómino, et exaltátum est cornu meum in Deo meo, quia lætáta sum in salutári tuo."
-  en: "My heart hath rejoiced in the Lord, * and my horn is exalted in my God: because I have joyed in thy salvation."
-status:
-  la: verified
-  en: verified

src/data/propers/common/immaculate-heart-of-mary-collect.yml

@@ -1,25 +0,0 @@
-# Read directly from web/www/horas/Latin/Sancti/08-22.txt's own
-# [Oratio] and its English counterpart.
-id: immaculate-heart-of-mary-collect
-text:
-  la: |
-    Orémus.
-    Omnípotens sempitérne Deus, qui in Corde beátæ Maríæ Vírginis dignum
-    Spíritus Sancti habitáculum præparásti: concéde propítius; ut ejúsdem
-    immaculáti Cordis festivitátem devóta mente recoléntes, secúndum Cor tuum
-    vívere valeámus.
-    Per Dóminum ejúsdem Fílii tui: qui tecum vivit et regnat in unitáte Spíritus
-    Sancti, Deus, per ómnia sǽcula sæculórum.
-    ℟. Amen.
-  en: |
-    Let us pray.
-    Almighty everlasting God, who hast prepared in the heart of Blessed Virgin
-    Mary a worthy dwelling of the Holy Ghost, grant favourably to us that we
-    may keep the feast of the same Immaculate Heart devoutly, and may be able
-    to live according to thy heart.
-    Through the same thy Son our Lord, Who liveth and reigneth with thee, in the
-    unity of the Holy Ghost, God, world without end.
-    ℟. Amen.
-status:
-  la: verified
-  en: verified