Bulk-author nameLa for all 299 remaining saints, close bilingual header backlog

Authors a real Latin nameLa for every saint in src/data/calendar/saints/
except the deliberate example-confessor placeholder (standard
ecclesiastical Latin forms, a lighter sourcing bar than this app's usual
reference-engine verification -- flagged for future spot-check). Fixes a
real mechanism bug found in the process: calendar/index.ts's sanctoral
collision-resolution branch was dropping nameLa for any saint that won
after beating another same-day candidate. Updates ~180 pre-existing test
fixtures across the calendar suite for the new field.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwsZQMjALCvy7u9tFDWmuQ

src/data/calendar/saints/our-lady-of-mount-carmel.yml

@@ -10,6 +10,7 @@
 # as our-lady-of-the-snows.yml/presentation-of-the-bvm.yml.
 id: our-lady-of-mount-carmel
 name: "Our Lady of Mount Carmel"
+nameLa: "Beata Maria Virgo de Monte Carmelo"
 rank: duplex-majus
 common: common-of-the-bvm
 propers: "our-lady-of-mount-carmel"