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/data/calendar/easter-offsets.yml

@@ -0,0 +1,18 @@
+# Offsets in days from Easter Sunday (0). Negative = before Easter, positive
+# = after. Covers the whole Easter-anchored span: Septuagesima through the
+# last Sunday of Trinitytide. A temporal-id's *name* (and hence whether it
+# reads "trinitytide" or "time after pentecost") lives here as data, not as
+# a compiled TS enum — see calendar/types.ts's Season type.
+#
+# PLACEHOLDER: only a handful of anchor points, to prove the shape. The full
+# set of Sundays/ferias between anchors is content-authoring work for
+# milestone 4.
+offsets:
+  -63: septuagesima-sunday
+  -56: sexagesima-sunday
+  -49: quinquagesima-sunday
+  -46: ash-wednesday
+  0: easter-sunday
+  39: ascension-thursday
+  49: pentecost-sunday
+  56: trinity-sunday