feat: scaffold monorepo with shared types and NestJS server

- pnpm workspace with packages/app, packages/server, packages/shared
- @mp-pilates/shared: enums, constants, TypeScript interfaces for all 8 data models
- @mp-pilates/server: NestJS bootstrap with health check, validation pipe, CORS
- Base TypeScript config with strict mode

packages/server/tsconfig.json

@@ -0,0 +1,18 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "dist",
+    "rootDir": "src",
+    "module": "CommonJS",
+    "moduleResolution": "node",
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "target": "ES2021",
+    "sourceMap": true,
+    "incremental": true,
+    "declaration": false,
+    "declarationMap": false
+  },
+  "include": ["src"],
+  "exclude": ["node_modules", "dist", "test"]
+}