Add vulnerability scan & triage workflow

Calls the reusable workflow from sourcebot-dev/sourcebot to run daily
Trivy, Dependabot, and CodeQL scanning with Claude-powered triage.

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

Author: msukkari

.github/workflows/vulnerability-triage.yml

@@ -0,0 +1,17 @@
+name: Vulnerability Triage
+
+on:
+  schedule:
+    - cron: '0 13 * * *'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  packages: read
+  security-events: read
+  id-token: write
+
+jobs:
+  triage:
+    uses: sourcebot-dev/sourcebot/.github/workflows/vulnerability-triage.yml@main
+    secrets: inherit