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/render_test.go

@@ -26,6 +26,11 @@ func TestRendererRendersEveryPage(t *testing.T) {
 		{"user_detail", UserDetailView{ID: "a1", DisplayName: "Kaya", HasStats: true, Stats: StatsRow{Wins: 2}, TelegramID: "123", ConnectorEnabled: true}, "Send Telegram message"},
 		{"user_detail", UserDetailView{ID: "a1", DisplayName: "Kaya", FlaggedHighRateAt: "2026-06-10 12:00"}, "Clear high-rate flag"},
 		{"user_detail", UserDetailView{ID: "a1", DisplayName: "Kaya", Roles: []string{"feedback_banned"}, KnownRoles: []string{"feedback_banned"}}, "feedback_banned"},
+		{"user_detail", UserDetailView{ID: "a1", DisplayName: "Kaya",
+			Friends:   []RelationRow{{AccountID: "b2", DisplayName: "Ann", Date: "2026-06-10 12:00"}},
+			Blocks:    []RelationRow{{AccountID: "c3", DisplayName: "Bob", Date: "2026-06-11 09:00"}},
+			BlockedBy: []RelationRow{{AccountID: "d4", DisplayName: "Cay", Date: "2026-06-12 08:00"}},
+		}, `/_gm/users/c3`},
 		{"throttled", ThrottledView{
 			Episodes:      []ThrottleEpisodeRow{{Class: "user", Key: "a1", UserID: "a1", Rejected: 1234, FirstSeen: "2026-06-10 12:00", LastSeen: "2026-06-10 12:05"}},
 			Flagged:       []FlaggedAccountRow{{ID: "a1", DisplayName: "Kaya", FlaggedAt: "2026-06-10 12:05"}},