feat(social): asymmetric per-user block, in-game block control, admin lists

Make a per-user block one-directional and non-destructive: the blocker stops
receiving everything from the blocked user (chat, nudge, friend requests,
invitations) and the matchmaker never pairs them, while the blocked user
notices nothing — their sends still persist by the normal rules but are never
delivered or surfaced (born-read). A block no longer deletes the friendship
(an unblock cleanly restores it) and instant-reads any unread the blocked user
had left for the blocker.

- backend: a directional blockExists guard across chat/nudge/friends/invitations
  (store-but-hide for the blocked->blocker direction, refuse blocker->blocked);
  the matchmaker excludes a block-related pair (both directions) from auto-match;
  user_blocked/user_unblocked notifications to the blocker only (in-app only).
- ui: the opponent score card gains a block ✖️ control mirroring add-friend
  (red "Block?" confirm, mutual-hide while confirming, struck name, hidden chat
  composer when blocked); optimistic apply + event confirm + rollback for both.
- admin: the user card gains cross-linked blocks / blocked-by / friends lists.
- docs: FUNCTIONAL(+ru), ARCHITECTURE §10 + decision record, UI_DESIGN, PRERELEASE.

backend/internal/adminconsole/views.go

@@ -175,6 +175,21 @@ type UserDetailView struct {
 	// grant form offers. The first role is the feedback ban (see internal/account).
 	Roles      []string
 	KnownRoles []string
+	// Blocks, BlockedBy and Friends are the social graph on the card: who this account has
+	// blocked, who currently blocks it, and its mutual friendships — each cross-linked to the
+	// other account with the date it happened. They are the full truth; the asymmetric block
+	// suppression that hides relationships from players never applies to the console.
+	Blocks    []RelationRow
+	BlockedBy []RelationRow
+	Friends   []RelationRow
+}
+
+// RelationRow is one cross-linked account in the user card's blocks / blocked-by / friends
+// lists: the other account's id (the link target), its display name, and the pre-formatted date.
+type RelationRow struct {
+	AccountID   string
+	DisplayName string
+	Date        string
 }
 
 // SuspensionView is an account's current manual-block state shown on the user card: whether it