Generate canonical and og:url from request path

[BenjaminMichaelis]

Why

The site metadata was inconsistent: og:url in _Layout.cshtml was hardcoded to the homepage, which did not match the actual route being viewed.

What changed

• Generate a request-specific absolute URL in _Layout.cshtml from the current path.
• Use that URL for both and .
• Include X-Forwarded-Host in forwarded header processing so host resolution is correct behind proxies.

Notes for reviewers

• This keeps the existing chapter head injection behavior while providing consistent layout-level metadata across routes.
• Query strings remain excluded because canonical/OG values are path-based.

[Copilot]

Pull request overview

Generates per-request canonical and og:url URLs in the shared layout instead of hardcoding the homepage, and enables X-Forwarded-Host so the host resolves correctly behind the reverse proxy.

Changes:

• Compute canonicalUrl from Request.Scheme, Request.Host, PathBase, and Path in _Layout.cshtml.
• Use canonicalUrl for both <meta property="og:url"> and a new <link rel="canonical">.
• Add ForwardedHeaders.XForwardedHost to the forwarded headers configuration.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
EssentialCSharp.Web/Views/Shared/_Layout.cshtml	Builds a request-specific canonical URL and uses it for og:url and a new canonical link tag.
EssentialCSharp.Web/Program.cs	Adds XForwardedHost to the accepted forwarded headers so Request.Host reflects the original host behind the proxy.

[BenjaminMichaelis]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Merge conflicts resolved in b18d7c0. The conflict in Program.cs was between the branch's inline ForwardedHeadersOptions configuration (which added XForwardedHost) and main's refactored AddTrustedForwardedHeaders extension method. I resolved this by using AddTrustedForwardedHeaders (from main) and adding XForwardedHost to that extension in IServiceCollectionExtensions.cs to preserve the canonical URL functionality. _Layout.cshtml merged cleanly with all canonical URL changes intact.