ci: add a nightly build

this is interesting for the functional testing of the tool

.gitea/workflows/nightly.yml

@@ -0,0 +1,35 @@
+name: Nightly Functional Tests
+
+on:
+  schedule:
+    # Runs every day at midnight UTC
+    - cron: '0 0 * * *'
+  workflow_dispatch:  # Allows manual trigger from the UI
+
+jobs:
+  functional:
+    runs-on: codeberg-small
+    steps:
+      - name: Checkout code
+        uses: https://github.com/actions/checkout@v4
+        with:
+          ref: main  # Always test the main branch
+
+      - name: Set up Go
+        uses: https://github.com/actions/setup-go@v5
+        with:
+          go-version: '1.21'
+          cache: true
+
+      - name: Build production binary
+        run: |
+          make build
+          echo "Binary built at: $(pwd)/bin/fgj"
+
+      - name: Run functional tests
+        run: go test -v -race -tags=functional ./tests/functional/...
+        env:
+          CODEBERG_TEST_TOKEN: ${{ secrets.CODEBERG_TEST_TOKEN }}
+          CODEBERG_TEST_OWNER: ${{ vars.CODEBERG_TEST_OWNER }}
+          CODEBERG_TEST_REPO: ${{ vars.CODEBERG_TEST_REPO }}
+          CODEBERG_TEST_HOSTNAME: ${{ vars.CODEBERG_TEST_HOSTNAME || 'codeberg.org' }}