Initial scaffold: unified customer/insurance/utilities platform

Next.js + NestJS + Prisma (MySQL) monorepo replacing the legacy PHP
internal app. Includes a session-based auth module with Argon2 password
hashing and global input validation (replacing the old app's SQL
injection and plaintext password comparison), the full target Prisma
schema for customers/insurance/utilities/shared ledger/bank register,
Docker Compose + Dockerfiles, and an Access-to-staging migration
pipeline (migration/) already run against the real source databases.

See PLAN.md and RESUME.md for the full architecture and session history.

apps/api/src/app.controller.ts

@@ -0,0 +1,9 @@
+import { Controller, Get } from "@nestjs/common";
+
+@Controller()
+export class AppController {
+  @Get("health")
+  health() {
+    return { status: "ok" };
+  }
+}