Milestone 0/1: shell, calendar/psalter/hours scaffold, Prime

Client-side-first PWA (Vite/TS, no backend) per the approved plan: day-
navigable shell listing all 8 hours, Prime fully resolves via the
calendar -> psalter -> ordo pipeline, the other 7 hours are registered
but flagged not-implemented. Sanctoral/temporal calendar data uses a
day -> id indirection layer (saints, easter-offsets, fixed-date-calendar)
so reassigning a feast to a different day is a data edit, not a code
change. Docker (Caddy-serving-static) + Gitea CI workflow scaffolded to
match the eec/drip/bookshop operational pattern.

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

src/calendar/easter.ts

@@ -0,0 +1,8 @@
+// Computus (the date of Easter, and everything the temporal cycle hangs off
+// of it — Septuagesima, Ash Wednesday, Ascension, Pentecost, Trinity Sunday).
+// Not implemented yet: unused until milestone 4 (Lauds/Vespers), which is the
+// first hour content that actually varies by season. Deliberately left empty
+// rather than half-built ahead of need — see the "content stores" section of
+// the plan for why calendar-rule logic is being kept swappable rather than
+// front-loaded.
+export {};