feat: add SonarCloud CI workflow

Replaces the GitHub App integration with a CI-based scan.
Scans astro-site/src on every PR and push to main.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: braboj

.github/workflows/sonarcloud.yml

@@ -0,0 +1,23 @@
+name: SonarCloud
+
+on:
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - main
+
+jobs:
+  sonarcloud:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: SonarCloud Scan
+        uses: SonarSource/sonarqube-scan-action@v5
+        env:
+          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

sonar-project.properties

@@ -0,0 +1,4 @@
+sonar.projectKey=braboj_tutorial-git
+sonar.organization=braboj
+sonar.sources=astro-site/src
+sonar.exclusions=**/node_modules/**,**/dist/**,**/.astro/**