Add 6 more April saints previously never added

St. Isidore of Seville, St. Vincent Ferrer, St. Hermenegild, St. Anselm,
St. Fidelis of Sigmaringen, St. Peter Canisius -- April complete.
St. Peter Canisius is the second common-of-a-confessor-doctor saint
(after St. John Damascene in March), same benedictusCommon reuse
pattern. St. Hugh, Abbot (Apr 1) checked and correctly skipped: his own
file is Commemoratio-rank with only a collect, no Lectio content at
all to source.

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

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

src/data/propers/common/st-hermenegild-collect.yml

@@ -0,0 +1,22 @@
+# Read directly from web/www/horas/Latin/Sancti/04-13.txt's own
+# [Oratio] and its English counterpart.
+id: st-hermenegild-collect
+text:
+  la: |
+    Orémus.
+    Deus, qui beátum Hermenegíldum Mártyrem tuum cælésti regno terrénum postpónere
+    docuísti: da quǽsumus nobis; ejus exémplo cadúca despícere, atque ætérna sectári.
+    Per Dóminum nostrum Jesum Christum, Fílium tuum: qui tecum vivit et regnat in unitáte
+    Spíritus Sancti, Deus, per ómnia sǽcula sæculórum.
+    ℟. Amen.
+  en: |
+    Let us pray.
+    O God, Who didst teach thy blessed Martyr Hermenegild to choose an heavenly rather
+    than an earthly crown, grant, we beseech thee, that we, like him, may so pass through
+    things temporal that we finally miss not those which are eternal.
+    Through Jesus Christ, 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