docs(readme): replace star-history.com with self-generated chart (#11171)

* docs(readme): replace star-history.com with self-generated chart

The star-history.com SVG is a third-party dependency that can rate
limit or go down. Replace it with a GitHub Action that fetches
stargazers via the REST API and renders an SVG with matplotlib,
committing note/star_history.svg weekly. The README references the
committed file directly, so the chart has no runtime dependency on
any external service.

* ci(star-history): run daily instead of weekly

.github/workflows/star_history.yml

@@ -0,0 +1,46 @@
+---
+name: Star History
+
+on:
+  schedule:
+    - cron: "0 0 * * *"  # daily, 00:00 UTC
+  workflow_dispatch:
+
+permissions:
+  contents: write
+
+jobs:
+  render:
+    name: Regenerate star history chart
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+
+      - name: Set up Python
+        uses: actions/setup-python@v8
+        with:
+          python-version: "3.x"
+          cache: pip
+          cache-dependency-path: .github/scripts/star_history.py
+
+      - name: Install matplotlib
+        run: pip install matplotlib
+
+      - name: Render chart
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: python .github/scripts/star_history.py
+
+      - name: Commit if changed
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          if git diff --quiet -- note/star_history.svg; then
+            echo "No changes to the chart."
+            exit 0
+          fi
+          git add note/star_history.svg
+          git commit -m "docs: regenerate star history chart"
+          git push