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>

.gitea/workflows/build.yml

@@ -0,0 +1,40 @@
+name: Build and push image
+
+on:
+  push:
+    branches: [main]
+    tags: ['v*']
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: docker/setup-buildx-action@v3
+
+      - uses: docker/login-action@v3
+        with:
+          registry: gitea.thewrightserver.net
+          username: ${{ gitea.repository_owner }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: gitea.thewrightserver.net/josh/apothecary
+          tags: |
+            type=ref,event=branch
+            type=sha,prefix=,format=short
+            type=semver,pattern={{version}}
+            type=raw,value=latest,enable={{is_default_branch}}
+
+      - uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max