fix(infra): resolve NestJS dist build and Prometheus target issues

NestJS: disable incremental in 6 services tsconfig.json to fix dist
not emitted when nest-cli deleteOutDir conflicts with tsc tsbuildinfo.
classes/iam: import HealthModule in AppModule to fix /healthz 404.
classes: rewrite HealthController to Drizzle getDb from TypeORM DI.
teacher-bff: add /metrics endpoint for Prometheus scraping.
infra: add node/mysql/redis exporters to observability profile.
mysql-exporter v0.15.1 uses command-line flags not DATA_SOURCE_NAME.
prometheus: enable web.enable-lifecycle for hot reload.

docs/standards/full-stack-runbook.md

@@ -195,6 +195,8 @@ Invoke-RestMethod -Uri "http://localhost:3006/readyz"
 ```powershell
 cd e:\Desktop\Edu
 .\scripts\stop-all.ps1
+
+.\scripts\stop-all.ps1 -KillByPort
 ```
 
 该脚本会关闭所有 `edu-app-*` 标题的终端窗口。