ci: attempt to fix e2e build step

Author: foosel

.github/workflows/build.yml

@@ -57,6 +57,8 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: OctoPrint/OctoPrint
+          ref: maintenance
+          fetch-depth: 0
           path: OctoPrint
 
       - name: ⬇ Download build result
@@ -72,19 +74,21 @@ jobs:
 
       - name: 🏗 Install OctoPrint
         run: |
-          cd OctoPrint
-          pip install .
-          pip install ${{ github.workspace }}/dist/*.whl
+          pip install OctoPrint
+          pip install --force-reinstall ${{ github.workspace }}/dist/*.whl
 
       - name: 🏗 Create base config for test server
         run: |
           mkdir e2econfig
           cp -r OctoPrint/.github/fixtures/with_acl/* e2econfig
 
-      - name: 🏗 Install dummy mfa plugin
+      - name: 🏗 Install dummy mfa plugin if available
         run: |
-          mkdir -p e2econfig/plugins
-          cp -r OctoPrint/.github/fixtures/mfa_dummy e2econfig/plugins/mfa_dummy
+          plugin="${{ github.workspace }}/OctoPrint/.github/fixtures/mfa_dummy"
+          if [ -f "$plugin" ]; then
+            mkdir -p e2econfig/plugins
+            cp -r "$plugin" "e2econfig/plugins/mfa_dummy"
+          fi
 
       - name: 🏗 Prepare Playwright env
         working-directory: ./OctoPrint/tests/playwright