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/account/userlist.go

@@ -51,11 +51,11 @@ func (s *Store) IsRobot(ctx context.Context, accountID uuid.UUID) (bool, error)
 func userListWhere(f UserFilter) (string, []any) {
 	args := []any{f.Robots}
 	where := robotExists + ` = $1`
-	if name := likePattern(f.NameMask); name != "" {
+	if name := LikePattern(f.NameMask); name != "" {
 		args = append(args, name)
 		where += fmt.Sprintf(` AND a.display_name ILIKE $%d ESCAPE '\'`, len(args))
 	}
-	if ext := likePattern(f.ExternalIDMask); ext != "" {
+	if ext := LikePattern(f.ExternalIDMask); ext != "" {
 		args = append(args, ext)
 		where += fmt.Sprintf(` AND EXISTS (SELECT 1 FROM backend.identities i WHERE i.account_id = a.account_id AND i.external_id ILIKE $%d ESCAPE '\')`, len(args))
 	}
@@ -95,9 +95,9 @@ func (s *Store) CountUsers(ctx context.Context, f UserFilter) (int, error) {
 	return n, nil
 }
 
-// likePattern converts a glob mask ('*' any run, '?' one char) to an ILIKE pattern,
+// LikePattern converts a glob mask ('*' any run, '?' one char) to an ILIKE pattern,
 // escaping the SQL wildcards already in the input first. An empty/blank mask returns "".
-func likePattern(mask string) string {
+func LikePattern(mask string) string {
 	mask = strings.TrimSpace(mask)
 	if mask == "" {
 		return ""