switched back to manual install of uv for testing

.gitea/workflows/backend_run_test.yaml

@@ -15,10 +15,10 @@ jobs:
 
     - uses: https://gitea.com/actions/checkout@v4
 
-    - name: Install uv (setup-uv)
-      uses: astral-sh/setup-uv@v6
-      with:
-        version: "latest"
+    - name: Install uv (manually)
+      run: |
+        curl -LsSf https://astral.sh/uv/install.sh | sh
+        echo "$HOME/.local/bin" >> $GITHUB_PATH
 
     - name: Install dependencies
       working-directory: backend