Profile and post pages, NodeInfo 2.1, and FEDERATION.md

/@user and /@user/{id} are Razor pages showing an avatar's or community's
public and unlisted posts: no scripts, a strict CSP, no-referrer, noindex,
and an alternate link to the ActivityPub document. A client asking them
for activity+json is redirected to the actor or note, and the actor and
note redirect browsers here.

NodeInfo answers 2.1 as well as 2.0 (repository, homepage, a link to
FEDERATION.md) and counts only public local posts.

FEDERATION.md (FEP-67ff) lists the protocols, FEPs, route names,
activities and the security rules a peer will notice.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub/Web/Pages/_ViewImports.cshtml

@@ -0,0 +1,3 @@
+@using PrivaPub.Web.Pages
+@namespace PrivaPub.Web.Pages
+@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers