fix(backend): set DATABASE_URL for prisma generate in docker build

backend/Dockerfile

@@ -7,7 +7,7 @@ RUN apk add --no-cache curl jq
 COPY package*.json ./
 COPY prisma ./prisma
 RUN npm ci
-RUN npx prisma generate
+RUN DATABASE_URL="postgresql://postgres:postgres@127.0.0.1:5432/postgres?schema=public" npx prisma generate
 
 COPY . .