Add automated broken link checking for documentation

.github/workflows/docs_link_check.yml

@@ -0,0 +1,66 @@
+name: Docs Broken Link Checker
+
+on:
+  pull_request:
+    paths:
+      - "site/content/docs/main/**/*.md"
+  # Run weekly
+  schedule:
+    - cron: "0 7 * * 1"
+
+  # Allow manual runs
+  workflow_dispatch:
+
+jobs:
+  link-check:
+    runs-on: ubuntu-latest
+
+    steps:
+      # Step 1: Checkout repository
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      # Step 2: Run Lychee link checker on MAIN docs only
+      - name: Run Lychee link checker (main docs only)
+        uses: lycheeverse/lychee-action@v1
+        with:
+          args: >
+            --verbose
+            --no-progress
+            --timeout 20
+            --max-retries 3
+            --retry-wait-time 5
+            --exclude-mail
+            --accept 200,206,429
+            --ignore-path .lycheeignore
+            --output lychee-report.md
+            --format markdown
+            "site/content/docs/main/**/*.md"
+
+      # Step 3: Check if an open broken-link issue already exists
+      # This prevents weekly issue spam.
+      - name: Check if issue already exists
+        if: failure() && github.event_name == 'schedule'
+        id: issue-check
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const query =
+              'repo:${{ github.repository }} ' +
+              'is:issue is:open ' +
+              '"Broken links detected in Contour documentation"';
+
+            const result = await github.rest.search.issuesAndPullRequests({
+              q: query
+            });
+
+            core.setOutput("exists", result.data.total_count > 0);
+
+      # Step 4: Create issue ONLY if none exists already
+      - name: Create GitHub issue (scheduled run only)
+        if: failure() && github.event_name == 'schedule' && steps.issue-check.outputs.exists == 'false'
+        uses: peter-evans/create-issue-from-file@v5
+        with:
+          title: "Broken links detected in Contour documentation"
+          content-filepath: lychee-report.md
+          labels: documentation, automated

.lycheeignore

@@ -0,0 +1,28 @@
+# Lychee Ignore File for Contour Documentation Link Checks
+
+# Purpose:
+# - Avoid false positives from placeholder/dev links
+# - Ignore dynamic GitHub URLs that cannot be validated reliably
+# - Reduce CI noise while still catching real broken links
+
+# Local development links (not valid in CI)
+localhost
+127.0.0.1
+
+# Placeholder/example domains used in docs
+example.com
+example.org
+
+# Mail links are not checkable as HTTP URLs
+mailto:*
+
+# GitHub issue creation links are dynamic and often return redirects
+https://github.com/projectcontour/contour/issues/new*
+https://github.com/projectcontour/contour/issues?q=*
+
+# GitHub compare URLs are temporary/dynamic
+https://github.com/projectcontour/contour/compare/*
+
+# Common documentation short-links that may rate-limit bots
+https://twitter.com/*
+https://x.com/*