feat: init fitness-coach (backend + miniprogram)

- backend: NestJS service with exercise/plan data
- miniprogram: WeChat mini program client
- exclude node_modules, dist, runtime data-store, local env

miniprogram/components/bottom-nav/index.json

@@ -0,0 +1,4 @@
+{
+  "component": true,
+  "usingComponents": {}
+}