Add Docker image, compose, and Gitea CI

- Multi-stage Dockerfile builds server + web into a single node:20-alpine
  image; runtime serves API on /api and the SPA from /app/public.
- Express now serves web/dist with an SPA fallback that skips /api so API
  misses still 404 cleanly.
- docker-compose.yml is a single-service deploy with a named volume for
  the SQLite database at /data/apothecary.db.
- .gitea/workflows/build.yml pushes :latest, :<sha>, and :semver tags to
  the Gitea container registry on main and v* tags.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,15 @@
+services:
+  apothecary:
+    image: gitea.thewrightserver.net/josh/apothecary:latest
+    container_name: apothecary
+    restart: unless-stopped
+    ports:
+      - "4000:4000"
+    environment:
+      PORT: "4000"
+      APOTHECARY_DB: /data/apothecary.db
+    volumes:
+      - apothecary-data:/data
+
+volumes:
+  apothecary-data: