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-fidelis-of-sigmaringen-collect.yml

@@ -0,0 +1,26 @@
+# Read directly from web/www/horas/Latin/Sancti/04-24.txt's own
+# [Oratio] and its English counterpart.
+id: st-fidelis-of-sigmaringen-collect
+text:
+  la: |
+    Orémus.
+    Deus, qui beátum Fidélem, seráphico spíritus ardóre succénsum, in veræ fídei
+    propagatióne martýrii palma et gloriósis miráculis decoráre dignátus es: ejus,
+    quǽsumus, méritis et intercessióne, ita nos per grátiam tuam in fide et caritáte
+    confírma; ut in servítio tuo fidéles usque ad mortem inveníri mereámur.
+    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.
+    God, Who didst vouchsafe to enkindle in blessed Fidelis the fire of thy Seraphim, and
+    to glorify his toil to give men a true knowledge of thee by the palm-branch of
+    martyrdom and by great signs and wonders, be entreated, we beseech thee, for his sake
+    and by his prayers, and so establish us in the knowledge and love of thee, that we
+    also, like him, may be found faithful even unto death in serving of thee.
+    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