ci: add workflow to fetch and commit GitHub stars daily

Runs on a nightly schedule, installs deps with uv, calls make
fetch_github_stars, and pushes an update commit only when the
star data file actually changed.

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/fetch-github-stars.yml

@@ -0,0 +1,39 @@
+name: Fetch GitHub Stars
+
+on:
+  schedule:
+    - cron: "0 0 * * *"
+
+permissions:
+  contents: write
+
+jobs:
+  fetch:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
+        with:
+          enable-cache: true
+
+      - name: Install dependencies
+        run: uv sync --group build
+
+      - name: Fetch GitHub stars
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: make fetch_github_stars
+
+      - name: Commit updated star data
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git add website/data/github_stars.json
+          if ! git diff --cached --quiet; then
+            git commit -m "chore: update GitHub stars data"
+            git push
+          fi