Add README

Explains what vu is and how to develop and run it in production, without referencing reground.org's specific infrastructure.

README.md

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+# vu
+
+A static, offline-first PWA for praying the Divine Office — Matins, Lauds, Prime, Terce, Sext,
+None, Vespers, and Compline — in bilingual Latin/English, for any given date.
+
+This isn't a reconstruction of any single historical breviary. It's a personal design that
+draws on several historical sources without reproducing any one of them exactly: hour
+structure chiefly from the Monastic Tridentinum (1617), precedence/rubrics from Divino
+Afflatu, and a calendar merged from both the Tridentine 1906 and Divino Afflatu calendars,
+with more generous handling of commemorations and octaves than any one historical rite used.
+See `CLAUDE.md` (gitignored, not shipped in this repo) or the project's own notes for the full
+rationale if you're extending it.
+
+There's no backend and no database — everything is a pre-built static bundle, and the app is
+designed to keep working fully offline once it's been loaded once.
+
+## Development
+
+Requires Node.js (developed against Node 20+).
+
+```sh
+npm install
+npm run dev        # start the Vite dev server
+npm run build       # type-check (tsc --noEmit) and produce a production build in dist/
+npm run preview     # serve the production build locally
+npm test            # run the test suite (vitest)
+```
+
+Run a single test file or a subset by name:
+
+```sh
+npx vitest run tests/hours/vespers.test.ts
+npx vitest run -t "some test name"
+```
+
+## Running in production
+
+The app is entirely static once built, so "running it" just means serving `dist/` — any static
+file host works, as long as it falls back to `index.html` for unknown paths (the app does its
+own client-side routing for URLs like `/2026-08-09/prime`).
+
+### Docker
+
+A `Dockerfile` builds the static bundle with Node and serves it with Caddy:
+
+```sh
+docker build -t vu .
+docker run -p 8080:80 vu
+```
+
+Or with Docker Compose (`docker-compose.yml` is included):
+
+```sh
+docker compose up -d --build
+```
+
+This serves the app on `http://localhost:8080`. Put a reverse proxy/TLS terminator in front of
+it for a real deployment; the container itself just listens on port 80 internally and has no
+configuration, secrets, or external dependencies.
+
+### Without Docker
+
+Any static file server works — build the app, then serve `dist/` with SPA-style fallback
+routing. For example, with Caddy directly:
+
+```sh
+npm run build
+caddy file-server --root dist --listen :8080
+```
+
+(For a real deployment you'll want a fallback rule so unknown paths resolve to `index.html` —
+see the `Caddyfile` in this repo for the pattern.)