epic: launch a versioned PayBridge documentation site on GitHub Pages

[teesofttech]

Outcome

Create an official, searchable, versioned documentation site hosted on GitHub Pages and linked from the repository and NuGet package.

Deliverables

• Getting started and installation.
• Configuration and secret-management guidance.
• Provider capability matrix and per-gateway guides.
• Create, verify, refund, webhook, and routing concepts.
• Generated .NET API reference.
• Testing, troubleshooting, migration, and contribution guides.
• Automated Pages deployment, link checking, and preview workflow.

Acceptance criteria

• A public Pages URL is enabled and uses HTTPS.
• The site is deployed from a reviewed GitHub Actions workflow.
• README, repository About, releases, and NuGet metadata link to it.
• Search, responsive navigation, accessibility, and version indication work.
• Documentation ownership and update policy are defined.
• Child documentation issues are linked from this epic.

[teesofttech]

Child backlog:

• docs: scaffold DocFX site with navigation, search, theme, and local authoring #79 Scaffold DocFX site
• docs: automate GitHub Pages deploys, previews, link checks, and version metadata #78 Automate Pages deployment and quality checks
• docs: publish a tested gateway capability and configuration matrix #80 Publish gateway capability/configuration matrix
• docs: add secure webhooks, idempotency, retries, and production-readiness guide #81 Add production-readiness and webhook security guide
• docs: correct README and NuGet claims to match the current implementation #84 Correct README and NuGet claims
• community: add issue forms, pull request template, code of conduct, and CODEOWNERS #85 Add community and ownership files