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/package.json

@@ -3,8 +3,8 @@
   "version": "1.0.0",
   "private": true,
   "scripts": {
-    "dev": "tsx watch src/app.ts",
-    "build": "tsc",
+    "dev": "npm run build --workspace=@calchat/shared && tsx watch src/app.ts",
+    "build": "npm run build --workspace=@calchat/shared && tsc",
     "start": "node dist/app.js",
     "test": "jest"
   },