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

packages/shared/package.json

@@ -2,11 +2,14 @@
   "name": "@calchat/shared",
   "version": "1.0.0",
   "private": true,
-  "main": "./src/index.ts",
-  "types": "./src/index.ts",
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
   "exports": {
-    ".": "./src/index.ts",
-    "./*": "./src/*"
+    ".": "./dist/index.js",
+    "./*": "./dist/*"
+  },
+  "scripts": {
+    "build": "tsc"
   },
   "dependencies": {
     "rrule": "^2.8.1"