FEDERATION.md and CLAUDE.md describe media, blocks, pins and reports

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

CLAUDE.md

@@ -90,6 +90,8 @@ PrivaPub/                         ASP.NET Core Web API, net10.0
     Social/                       FollowService (local in-process, remote Follow/Accept), Notifications
     Timelines/                    Fanout (TimelineEntry rows, Mastodon's home rules), TimelineService
     Privacy/                      VisibilityPolicy (IsPublic expression, CanSee)
+    Relationships/                RelationshipService (blocks, mutes, account domain blocks; Hidden), ReportService
+    Media/                        MediaService (libvips, ffmpeg remux, blurhash), MediaProxy, MediaJanitor
   Domain/Statuses/                StatusService: publish, edit, remove, favourite, reblog, for a persona (both client APIs use it)
   Api/Mastodon/
     Auth/                         OpenIddict setup (keys in Mongo), MastodonScopes, TokenController, OAuthPruner
@@ -190,6 +192,15 @@ cd /var/www/privapub.thepra.dev && sudo -u www-data ASPNETCORE_ENVIRONMENT=Produ
 5. Unsupported features answer empty lists or 422 with a message, never 404 or 500, so clients degrade.
 6. Advertise `4.2.0 (compatible; PrivaPub)` until grouped notifications exist.
 
+## Media invariants
+
+1. **No upload keeps its metadata.** Images are re-encoded by libvips with `keep=none`; audio and video are remuxed with
+   `-map_metadata -1`. `MediaProcessingTests` checks EXIF and XMP are gone.
+2. Files live under `Media:Root` (`/var/lib/privapub/media`), never in the published directory; the proxy cache is the
+   sibling `media-proxy`, which `/media/files` does not serve.
+3. **A client never contacts a remote server for media:** every remote URL the API returns goes through
+   `IMediaProxy.Wrap`, an HMAC-signed `/media/proxy/` URL fetched by `IFederationHttp.GetMedia`.
+
 ## Privacy invariants
 
 - **No root id in federation output, NodeInfo or logs, no IP next to an identity in logs, and no `ex.Message` to a
@@ -199,6 +210,7 @@ cd /var/www/privapub.thepra.dev && sudo -u www-data ASPNETCORE_ENVIRONMENT=Produ
 - **One username space:** personas, groups and the instance reserve their name in `ReservedName` (unique index) before
   they are saved; `LocalActorService.TryReserveUserName` is the only way to claim one.
 - **Per-avatar state stays per avatar:** blocks, mutes, notifications, follows. Nothing may relate sibling avatars.
+- **Blocks never federate,** and reports leave as `Flag` from the instance actor.
 - **Location-ranged posts never federate.**
 
 ## Data