Stage 17 round 6 (#18, PR D): admin Messages moderation section

A new /_gm/messages console page lists posted chat messages (nudges
excluded) newest-first — time, source (guest/robot/oldest identity kind),
sender (linked to the user card), IP, body, game (linked to the game card)
— searchable by sender name / external-id glob masks and pinnable to one
game (?game=) or sender (?user=), linked from the game and user cards.

The list query lives in social (raw SQL, kind='message', source via a SQL
CASE), reusing the now-exported account.LikePattern. Server-rendered
adminconsole MessagesView + messages.gohtml, 50/page via the shared pager.

Tests: adminconsole render case; backend integration AdminListMessages
(real Postgres) — nudge exclusion, game/sender pins, glob masks, source.
Docs: ARCHITECTURE section 8 chat moderation, PLAN round-6.

backend/internal/adminconsole/render_test.go

@@ -26,6 +26,7 @@ func TestRendererRendersEveryPage(t *testing.T) {
 		{"games", GamesView{Items: []GameRow{{ID: "g1", Variant: "english", Status: "active"}}, Status: "active", Pager: NewPager(1, 50, 1)}, "g1"},
 		{"game_detail", GameDetailView{ID: "g1", Variant: "english", Seats: []SeatRow{{Seat: 0, DisplayName: "Kaya"}}}, "Seats"},
 		{"complaints", ComplaintsView{Items: []ComplaintRow{{ID: "c1", Word: "qi", Status: "open"}}, Status: "open", Pager: NewPager(1, 50, 1)}, "qi"},
+		{"messages", MessagesView{Items: []MessageRow{{ID: "m1", SenderID: "a1", SenderName: "Kaya", Source: "telegram", Body: "good luck", GameID: "g1"}}, Pager: NewPager(1, 50, 1)}, "good luck"},
 		{"complaint_detail", ComplaintDetailView{ID: "c1", Word: "qi", Variant: "english"}, "Resolve"},
 		{"dictionary", DictionaryView{Variants: []VariantVersions{{Variant: "english", Latest: "v1", Versions: []string{"v1"}}}, Changes: []DictChangeRow{{Variant: "english", Word: "qi", Action: "add"}}}, "Hot-reload"},
 		{"broadcast", BroadcastView{ConnectorEnabled: true}, "Post to the game channel"},