ci: configure Forgejo git credentials before pip install

FORGEJO_TOKEN secret injected via env var (not inline expression) to
avoid CI injection risk; git insteadOf redirect authenticates the
git+https:// circuitforge-core VCS URL at install time.

.github/workflows/ci.yml

@@ -22,6 +22,12 @@ jobs:
           python-version: "3.11"
           cache: pip
 
+      - name: Configure git credentials for Forgejo
+        env:
+          FORGEJO_TOKEN: ${{ secrets.FORGEJO_TOKEN }}
+        run: |
+          git config --global url."https://oauth2:${FORGEJO_TOKEN}@git.opensourcesolarpunk.com/".insteadOf "https://git.opensourcesolarpunk.com/"
+
       - name: Install dependencies
         run: pip install -r requirements.txt