fix: set NODE_ENV=development in sync builder to install devDependencies

node:20-slim defaults NODE_ENV=production which causes npm to skip dev
deps (typescript, ts-node), preventing tsc from being found.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

sync/Dockerfile

@@ -2,7 +2,7 @@
 FROM node:20-slim AS builder
 WORKDIR /app
 COPY package.json package-lock.json ./
-RUN npm install
+RUN NODE_ENV=development npm install
 COPY tsconfig.json ./
 COPY src ./src
 RUN ./node_modules/.bin/tsc && npm prune --production