chore: change PostgreSQL host port to 5433

Avoids conflict with other local Postgres instances.
Container internal port stays 5432; only the host-side mapping changes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/docker-compose.yml

@@ -6,7 +6,7 @@ services:
       POSTGRES_USER: food_ai
       POSTGRES_PASSWORD: food_ai_local
     ports:
-      - "5432:5432"
+      - "5433:5432"
     volumes:
       - pgdata:/var/lib/postgresql/data
     healthcheck: