Fix Docker Compose: add PYTHONPATH for Alembic, use port 8100, fix Vite proxy for container networking

docker-compose.yml

@@ -18,15 +18,17 @@ services:
   backend:
     build: ./backend
     ports:
-      - "8000:8000"
+      - "8100:8000"
     env_file: ./backend/.env
     depends_on:
       - db
       - redis
+    working_dir: /app
+    environment:
+      - PYTHONPATH=/app
     command: >
       sh -c "
         pip install alembic psycopg2-binary &&
-        cd /app &&
         alembic upgrade head &&
         uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload
       "