Implement comprehensive link checker with image focus and CI/CD integration

[Copilot]

This PR implements a comprehensive link checking system for the OrionRobots website with a focus on detecting broken image links and internal link issues, addressing the need for automated link validation as outlined in the issue.

Key Features

🎯 Image-Focused Link Checking

• Prioritizes broken image links that affect visual content
• Categorizes links by type: images (high priority), internal links (high priority), external links (medium priority), and email links (low priority)
• Generates professional HTML reports with clear priority indicators

🐳 Docker Integration

• Enhanced Docker container based on Ubuntu 22.04 with linkchecker, Python 3, and Jinja2
• Integrated with existing docker-compose.yml using the manual profile
• Health checks and proper volume mounting for report generation
• Robust error handling that continues checking even when broken links are found

🚀 Multiple Usage Options

• Local development: Simple ./scripts/local_linkcheck.sh script for manual execution
• PR validation: Triggered by adding the link-check label to pull requests
• Production monitoring: Automated nightly runs at 2 AM UTC via GitHub Actions
• Manual Docker: docker compose --profile manual up broken_links

📊 Professional Reporting

• Styled HTML reports with categorized broken links
• CSV output for programmatic analysis
• Clear priority-based organization helping developers focus on critical issues first
• Summary statistics showing counts by category

Implementation Details

The solution builds upon the existing draft linkchecker setup in _drafts/linkchecker/ and enhances it significantly:

1. Enhanced Python filtering script (linkchecker/filter_csv.py) that categorizes links and generates rich HTML reports
2. Comprehensive configuration (linkchecker/linkchecker.conf) optimized for the OrionRobots site
3. GitHub Actions workflows for both nightly monitoring and PR-based validation
4. Complete documentation including technical README and quick start guide

CI/CD Integration

Nightly Link Checking:

• Runs automatically against the production site (https://orionrobots.co.uk)
• Uploads detailed reports as GitHub Actions artifacts
• Creates warnings when broken links are detected
• Escalates to errors when many broken links are found

PR-Based Link Checking:

• Triggered when a PR is labeled with link-check
• Builds the site locally and runs link checking against the build
• Comments results directly on the PR with broken link details
• Provides actionable feedback for developers

Usage Examples

# Local development - one command execution
./scripts/local_linkcheck.sh

# Manual Docker usage
docker compose --profile manual up broken_links
open link_reports/link_check_report.html

# PR validation - just add the 'link-check' label

The implementation addresses all requirements from the issue:

• ✅ Wraps the link checking docker setup for internal broken links view
• ✅ Focuses on image links to help deal with broken images
• ✅ Provides nightly runs on the real site
• ✅ Enables PR runs when link-check label is added with proper teardown
• ✅ Offers optional/manual docker compose command locally

Fixes #216.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[github-actions]

🦙 MegaLinter status: ❌ ERROR

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
❌ ACTION	actionlint	7		2	0	0.07s
✅ BASH	bash-exec	3		0	0	0.01s
❌ BASH	shellcheck	3		1	0	0.13s
⚠️ BASH	shfmt	3		3	0	0.0s
❌ C	cppcheck	8		8	0	0.27s
❌ CPP	cppcheck	8		8	0	0.33s
✅ JSON	npm-package-json-lint	yes		no	no	0.47s
✅ JSON	v8r	12		0	0	9.42s
❌ MARKDOWN	markdown-link-check	738		213	0	35.22s
⚠️ PYTHON	black	1		1	0	0.59s
❌ PYTHON	flake8	1		11	0	0.52s
✅ PYTHON	mypy	1		0	0	2.95s
✅ REPOSITORY	gitleaks	yes		no	no	14.77s
✅ REPOSITORY	git_diff	yes		no	no	1.16s
✅ REPOSITORY	grype	yes		no	no	35.58s
✅ REPOSITORY	secretlint	yes		no	no	43.76s
✅ REPOSITORY	syft	yes		no	no	2.0s
✅ REPOSITORY	trivy-sbom	yes		no	no	3.43s
✅ REPOSITORY	trufflehog	yes		no	no	4.64s
✅ XML	xmllint	1		0	0	188.67s
✅ YAML	v8r	14		0	0	6.16s

See detailed report in MegaLinter reports

[dannystaple]

Can we remove the copy of this linkchecker folder from the _drafts folder?

[Copilot]

Done! Removed the outdated linkchecker copy from _drafts/linkchecker/ since the comprehensive implementation is now in .github/linkchecker/. Commit c0a7eed