So mit neuen UI Ideen und so

docs/ARCHITECTURE.md

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+Architecture Overview
+
+Layers
+- Domain: Types in `shared/` reused by backend/frontend.
+- Use-Cases: `backend/src/usecases` (e.g., auth/loginUser, employees CRUD, users management).
+- Repositories: `backend/src/repositories` do all DB access; controllers do not use SQL.
+- Adapters/HTTP: `backend/src/routes/*` map HTTP <-> use-cases and validate inputs.
+- Infra/Services: encryption, email, sync components, logger.
+
+Security
+- JWT required; in production `JWT_SECRET` must be set.
+- Field-level encryption (AES) for sensitive data + deterministic hashes for lookups.
+- Error redaction: sensitive fields are redacted in logs.
+
+Sync
+- Modular components under `backend/src/services/sync`:
+  - `queueStore`: DB interactions (pending, status, metadata)
+  - `transport`: HTTP communication between nodes
+  - `applier`: applies changes entity-wise
+  - `SyncService`: orchestrates and exposes routes
+
+Migrations
+- Simple runner: `npm run migrate` in `backend`
+- Tracks applied migrations in `schema_version`; add files to `backend/scripts/migrations`.
+
+Frontend
+- API abstraction with normalized error handling
+- ErrorBoundary wraps the app
+