Add 6 more February saints/feasts previously never added

Purification of the BVM (Feb 2), St. Andrew Corsini (Feb 4), St. John
of Matha (Feb 8), Apparition of the Immaculate BVM at Lourdes (Feb 11),
Ss. Seven Founders of the Servite Order (Feb 12), St. Gabriel of Our
Lady of Sorrows (Feb 27) -- all had real, complete Matins content in
the reference engine and no exclusion comment; simply never reached
during the earlier month-by-month sanctoral pulls. Continuing the same
sweep as January's St. Francis de Sales/St. Martina/St. John Bosco.

Test update (not a regression): St. Andrew Corsini transfers onto Feb 5
in years where Sexagesima falls on his own Feb 4, outranking St. Agatha
when it does -- february-sanctoral.test.ts's proof year for Agatha
moved from 2029 (now a collision year) to 2025 (clean).

npm test (365 tests) and tsc --noEmit both pass.

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

src/data/calendar/saints/apparition-of-the-immaculate-bvm.yml

@@ -0,0 +1,13 @@
+# Read directly from the reference engine: untagged/default [Rank]
+# block of `web/www/horas/Latin/Sancti/02-11.txt` -- "In Apparitione
+# Beatæ Mariæ Virginis Immaculatæ;;Duplex majus;;4;;ex C11" (Our Lady of
+# Lourdes). Own proper [Oratio]/[Ant 1]/Nocturn 2 vita (the Bernadette
+# apparition narrative); her Nocturn 3 is a direct `@Sancti/12-10bmv`
+# cross-reference -- shares content with the 3rd day within the Octave
+# of the Immaculate Conception (a different reading than
+# immaculate-conception.yml's own Dec 8 Nocturn 2 content).
+id: apparition-of-the-immaculate-bvm
+name: "The Apparition of the Immaculate Blessed Virgin Mary (Our Lady of Lourdes)"
+rank: duplex-majus
+common: common-of-the-bvm
+propers: "apparition-of-the-immaculate-bvm"