CI rename action as test;use volume for uv cache

.forgejo/workflows/install.yaml

@@ -1,17 +0,0 @@
-on: [push]
-jobs:
-  install:
-    runs-on: container
-    container:
-      image: tiptop:5000/treetrail-backend-ci-base
-    services:
-      treetrail-database:
-        image: treetrail-database
-    steps:
-    - uses: actions/checkout@v4
-    - name: Create venv
-      run: uv venv
-    - name: Install dependencies
-      run: uv sync
-    - name: Run basic test (bootstrap)
-      run: .venv/bin/pytest -s tests/basic.py