Initial commit: Mathe-App Phase 1-3

- React+Vite Frontend mit Routing, eigenem fetch-Client (kein axios)
- Express Backend: Auth (JWT), Topics, Tasks, Leaderboard
- PostgreSQL Schema + Seed: 7 Kategorien, 21 Topics, ~25 Aufgaben
- Gamification: XP, Level (100×n^1.5), tägliche Streaks
- docker-compose auf Port 3100 für DS1621
- Alltagsaufgaben: Finanzen, Geometrie, Physik, Informatik, Verkehr, Shopping

docker-compose.yml

@@ -0,0 +1,40 @@
+services:
+  frontend:
+    build:
+      context: ./frontend
+      dockerfile: ../docker/Dockerfile.frontend
+    ports:
+      - "3100:80"
+    depends_on:
+      - backend
+    restart: unless-stopped
+
+  backend:
+    build:
+      context: ./backend
+      dockerfile: ../docker/Dockerfile.backend
+    env_file: .env
+    depends_on:
+      db:
+        condition: service_healthy
+    restart: unless-stopped
+
+  db:
+    image: postgres:16-alpine
+    env_file: .env
+    environment:
+      POSTGRES_DB: ${DB_NAME}
+      POSTGRES_USER: ${DB_USER}
+      POSTGRES_PASSWORD: ${DB_PASSWORD}
+    volumes:
+      - pgdata:/var/lib/postgresql/data
+      - ./docker/init.sql:/docker-entrypoint-initdb.d/init.sql
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U ${DB_USER} -d ${DB_NAME}"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+    restart: unless-stopped
+
+volumes:
+  pgdata: