feat: add Docker support and compile shared package to dist

- Add multi-stage Dockerfile for server containerization
- Add .dockerignore to exclude unnecessary files from build context
- Switch shared package from source to compiled CommonJS output (dist/)
- Server dev/build scripts now build shared package first
- Fix deep imports to use @calchat/shared barrel export
- Update CLAUDE.md with Docker and shared package documentation

apps/server/docker/Dockerfile

@@ -0,0 +1,29 @@
+FROM node:alpine AS build
+
+WORKDIR /app
+
+COPY package.json package-lock.json tsconfig.json ./
+COPY packages/shared/ packages/shared/
+COPY apps/server/ apps/server/
+
+RUN npm ci --workspace=@calchat/server --workspace=@calchat/shared --include-workspace-root
+
+RUN npm run build --workspace=@calchat/shared && \
+    npm run build --workspace=@calchat/server
+
+FROM node:alpine
+
+WORKDIR /app
+
+COPY package.json package-lock.json ./
+COPY packages/shared/package.json packages/shared/
+COPY apps/server/package.json apps/server/
+
+RUN npm ci --omit=dev --workspace=@calchat/server --workspace=@calchat/shared --include-workspace-root
+
+COPY --from=build /app/packages/shared/dist/ packages/shared/dist/
+COPY --from=build /app/apps/server/dist/ apps/server/dist/
+
+EXPOSE 3000
+
+CMD ["node", "apps/server/dist/app.js"]