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/calendar/saints/immaculate-heart-of-mary.yml

@@ -1,13 +0,0 @@
-# Read directly from the reference engine: untagged/default [Rank]
-# block of `web/www/horas/Latin/Sancti/08-22.txt` -- "Immaculati Cordis
-# Beatæ Mariæ Virginis;;Duplex II classis;;5.1;;ex C11". Own real
-# [Oratio] and own [Ant 1]. Own Nocturn 2-3 content (Nocturn 3 is St.
-# Robert Bellarmine's own homily on the seven words of Christ on the
-# Cross, not a cross-reference). Instituted 1942 by Pius XII (see the
-# feast's own Lectio6, quoted in nocturn-readings, drawn from
-# ecclesiastical documents).
-id: immaculate-heart-of-mary
-name: "The Immaculate Heart of the Blessed Virgin Mary"
-rank: duplex-2-classis
-common: common-of-the-bvm
-propers: "immaculate-heart-of-mary"