ci: remove stale .github/workflows/ci.yml

The .forgejo/workflows/ci.yml is the canonical CI definition.
The old .github/workflows/ci.yml was being mirrored to GitHub via
--mirror push, triggering GitHub Actions runs that fail because
FORGEJO_TOKEN and other Forgejo-specific secrets are not set there.

GitHub Actions does not process .forgejo/workflows/ so removing
this file stops the spurious GitHub runs. ISSUE_TEMPLATE and
pull_request_template.md are preserved in .github/.

.github/workflows/ci.yml

@@ -1,35 +0,0 @@
-name: CI
-
-on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
-
-jobs:
-  test:
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Install system dependencies
-        run: sudo apt-get update -q && sudo apt-get install -y libsqlcipher-dev
-
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          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
-
-      - name: Run tests
-        run: pytest tests/ -v --tb=short