docs: add wiki page

Architektur.md

@@ -0,0 +1,70 @@
+# Architektur
+
+## Monorepo-Struktur
+
+```
+michess/
+├── client/          # Next.js 14 Frontend
+├── server/          # Express.js Backend
+├── types/           # Gemeinsame TypeScript-Typen (@michess/types)
+├── docker-compose.yml
+├── Dockerfile
+└── pnpm-workspace.yaml
+```
+
+## Client (`client/src/`)
+
+```
+app/                 # Next.js App Router (Seiten)
+├── page.tsx         # Startseite
+├── [code]/          # Aktive Partie
+├── archive/[id]/    # Archivierte Partie (PGN-Viewer)
+├── ai/              # KI-Partie
+├── correspondence/  # Tagespartien
+├── tournament/      # Turniere
+├── friends/         # Freunde
+├── user/[name]/     # Nutzerprofil
+├── settings/        # Kontoeinstellungen
+└── admin/           # Admin-Panel
+
+components/          # Wiederverwendbare Komponenten
+├── game/            # Spielbrett, Züge, Socket-Events
+├── home/            # Startseite-Karten
+├── Header.tsx       # Navigation + Benachrichtigungsglocke
+├── NotificationPanel.tsx  # Benachrichtigungs-Dropdown
+└── AuthModal.tsx    # Login/Register/Gast-Modal
+
+context/
+├── session.ts          # Nutzer-Session (global)
+├── ContextProvider.tsx # Wrapper für alle Contexts
+└── NotificationContext.tsx  # Echtzeit-Benachrichtigungen
+```
+
+## Server (`server/src/`)
+
+```
+controllers/         # Business-Logik
+db/
+├── index.ts         # DB-Verbindung + INIT_TABLES
+└── models/          # Datenbankmodelle
+middleware/
+├── auth.ts          # requireAuth, requireAdmin
+└── session.ts       # express-session
+routes/              # Express-Router
+socket/
+├── index.ts         # Socket.io-Verbindungen, Online-Tracking
+├── game.socket.ts   # Spielereignisse
+└── state.ts         # Gemeinsamer Socket-Zustand
+server.ts            # Einstiegspunkt
+```
+
+## Datenfluss
+
+```
+Browser ──HTTP──> Next.js (SSR/CSR)
+         ──API──> Express /v1/...
+         ──WS───> Socket.io (Echtzeit)
+                     │
+               PostgreSQL (pg.Pool)
+               Stockfish (child_process)
+```