fix: collab-server Dockerfile use multi-stage build for TypeScript

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

collab-server/Dockerfile

@@ -1,12 +1,21 @@
+FROM node:22-alpine AS builder
+
+WORKDIR /app
+
+COPY package.json package-lock.json* ./
+RUN npm install
+
+COPY . .
+RUN ./node_modules/.bin/tsc
+
 FROM node:22-alpine
 
 WORKDIR /app
 
 COPY package.json package-lock.json* ./
-RUN npm install --production
+RUN npm install --omit=dev
 
-COPY . .
-RUN npx tsc
+COPY --from=builder /app/dist ./dist
 
 EXPOSE 4000