Fix CI failures for backend and e2e test jobs

Replace astral-sh/setup-uv action with direct curl install to avoid
Node.js 18 incompatibility (setup-uv v6+ requires Node 20+). Change
e2e test API host port from 8000 to 8100 to avoid conflict with
existing service on the CI runner.

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

docker-compose.test.yml

@@ -21,7 +21,7 @@ services:
       context: ./backend
       dockerfile: Dockerfile
     ports:
-      - "8000:8000"
+      - "8100:8000"
     environment:
       - DATABASE_URL=postgresql+asyncpg://postgres:postgres@test-db:5432/nuzlocke_test
       - DEBUG=true