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/app-state.ts

@@ -0,0 +1,64 @@
+import type { HourId } from './hours/types';
+import type { LanguageCode } from './psalter/types';
+
+export interface AppState {
+  date: string; // ISO YYYY-MM-DD
+  selectedHour: HourId;
+  /** Exactly one or two entries — see plan: one-language / two-language layout only. */
+  languages: [LanguageCode] | [LanguageCode, LanguageCode];
+}
+
+export function todayIso(): string {
+  const d = new Date();
+  const yyyy = d.getFullYear();
+  const mm = String(d.getMonth() + 1).padStart(2, '0');
+  const dd = String(d.getDate()).padStart(2, '0');
+  return `${yyyy}-${mm}-${dd}`;
+}
+
+const state: AppState = {
+  date: todayIso(),
+  selectedHour: 'prime',
+  languages: ['en'],
+};
+
+type Listener = (state: Readonly<AppState>) => void;
+const listeners = new Set<Listener>();
+
+export function getState(): Readonly<AppState> {
+  return state;
+}
+
+export function subscribe(listener: Listener): () => void {
+  listeners.add(listener);
+  return () => listeners.delete(listener);
+}
+
+function notify(): void {
+  for (const listener of listeners) listener(state);
+}
+
+export function setDate(date: string): void {
+  state.date = date;
+  notify();
+}
+
+export function goToToday(): void {
+  setDate(todayIso());
+}
+
+export function shiftDate(days: number): void {
+  const d = new Date(`${state.date}T00:00:00Z`);
+  d.setUTCDate(d.getUTCDate() + days);
+  setDate(d.toISOString().slice(0, 10));
+}
+
+export function setSelectedHour(hourId: HourId): void {
+  state.selectedHour = hourId;
+  notify();
+}
+
+export function setLanguages(languages: AppState['languages']): void {
+  state.languages = languages;
+  notify();
+}