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>

.github/workflows/ci.yml

@@ -42,14 +42,15 @@ jobs:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4.3.1
         with:
           persist-credentials: false
-      - uses: astral-sh/setup-uv@d0cc045d04ccac9d8b7881df0226f9e82c39688e  # v6.8.0
-        with:
-          python-version: "3.14"
+      - name: Install uv and Python
+        run: |
+          curl -LsSf https://astral.sh/uv/install.sh | sh
+          uv python install 3.14
       - name: Install dependencies
-        run: uv pip install --system -e ".[dev]"
+        run: uv pip install --system --python 3.14 -e ".[dev]"
         working-directory: backend
       - name: Run tests
-        run: pytest -q
+        run: uv run --python 3.14 pytest -q
         working-directory: backend
         env:
           TEST_DATABASE_URL: postgresql+asyncpg://postgres:postgres@localhost:5433/nuzlocke_test