fix(docker): fix data volume ownership on fresh bind mounts

/app/data is a bind mount, so the chown baked into the image is
overwritten by the host directory's ownership at runtime. On a fresh
prod deploy Docker creates ./data as root-owned, but the container ran
as the non-root nextjs user, so Prisma couldn't open lovelope.db
("unable to open database file").

Add an entrypoint that starts as root, chowns /app/data, then drops to
nextjs via su-exec before running migrations and starting the server.

Dockerfile

@@ -28,7 +28,7 @@ RUN npm run build
 
 # ── Stage 3: runner ────────────────────────────────────────────────────────────
 FROM node:20-alpine AS runner
-RUN apk add --no-cache libc6-compat openssl
+RUN apk add --no-cache libc6-compat openssl su-exec
 WORKDIR /app
 
 ENV NODE_ENV=production
@@ -48,11 +48,11 @@ COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
 
 RUN mkdir -p /app/data && chown nextjs:nodejs /app/data
 
-USER nextjs
+COPY --chmod=755 docker-entrypoint.sh ./docker-entrypoint.sh
 
 EXPOSE 3000
 ENV PORT=3000
 ENV HOSTNAME="0.0.0.0"
 
-# Run migrations then start the server
-CMD ["sh", "-c", "npx prisma migrate deploy && node server.js"]
+# Fix ownership of the bind-mounted /app/data volume, then drop to nextjs
+ENTRYPOINT ["./docker-entrypoint.sh"]

docker-entrypoint.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+set -e
+
+chown -R nextjs:nodejs /app/data
+
+exec su-exec nextjs sh -c "npx prisma migrate deploy && node server.js"