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.

.gitignore

@@ -0,0 +1,14 @@
+node_modules/
+.next/
+dist/
+build/
+.env
+.env.*
+!.env.example
+*.log
+migration/output/
+migration/.venv/
+__pycache__/
+*.pyc
+packages/database/generated/
+.DS_Store