Set build-time DATABASE_URL for Prisma generate

Dockerfile

@@ -5,6 +5,7 @@ WORKDIR /app
 COPY package*.json ./
 COPY prisma ./prisma
 COPY prisma.config.ts ./
+ENV DATABASE_URL=postgresql://postgres:postgres@localhost:5432/fregat
 RUN npm ci && npx prisma generate
 
 COPY src ./src