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/templates/layout.gohtml

@@ -16,6 +16,7 @@
     <a href="/_gm/users"{{if eq .ActiveNav "users"}} class="active"{{end}}>Users</a>
     <a href="/_gm/games"{{if eq .ActiveNav "games"}} class="active"{{end}}>Games</a>
     <a href="/_gm/complaints"{{if eq .ActiveNav "complaints"}} class="active"{{end}}>Complaints</a>
+    <a href="/_gm/messages"{{if eq .ActiveNav "messages"}} class="active"{{end}}>Messages</a>
     <a href="/_gm/dictionary"{{if eq .ActiveNav "dictionary"}} class="active"{{end}}>Dictionary</a>
     <a href="/_gm/broadcast"{{if eq .ActiveNav "broadcast"}} class="active"{{end}}>Broadcast</a>
     <a href="/_gm/grafana/">Grafana ↗</a>

backend/internal/adminconsole/templates/pages/game_detail.gohtml

@@ -1,7 +1,7 @@
 {{define "content" -}}
 {{with .Data}}
 <h1>Game {{.ID}}</h1>
-<nav class="subnav"><a href="/_gm/games">&laquo; games</a></nav>
+<nav class="subnav"><a href="/_gm/games">&laquo; games</a> · <a href="/_gm/messages?game={{.ID}}">messages</a></nav>
 <section class="panel"><h2>Summary</h2>
 <ul class="kv">
 <li><b>Variant</b> {{.Variant}}</li>

backend/internal/adminconsole/templates/pages/messages.gohtml

@@ -0,0 +1,37 @@
+{{define "content" -}}
+<h1>Messages</h1>
+{{with .Data}}
+<form class="form" method="get" action="/_gm/messages">
+{{if .GameID}}<input type="hidden" name="game" value="{{.GameID}}">{{end}}
+{{if .UserID}}<input type="hidden" name="user" value="{{.UserID}}">{{end}}
+<input name="name" value="{{.NameMask}}" placeholder="sender name mask (* ?)">
+<input name="ext" value="{{.ExtMask}}" placeholder="sender external id mask (* ?)">
+<button type="submit">Filter</button>
+</form>
+{{if or .GameID .UserID}}
+<p class="note">Filtered{{if .GameID}} to game <a href="/_gm/games/{{.GameID}}">{{.GameID}}</a>{{end}}{{if .UserID}} from <a href="/_gm/users/{{.UserID}}">sender</a>{{end}} · <a href="/_gm/messages">clear</a></p>
+{{end}}
+<table class="list">
+<thead><tr><th>Time</th><th>Source</th><th>Sender</th><th>IP</th><th>Message</th><th>Game</th></tr></thead>
+<tbody>
+{{range .Items}}
+<tr>
+<td>{{.CreatedAt}}</td>
+<td>{{.Source}}</td>
+<td><a href="/_gm/users/{{.SenderID}}">{{.SenderName}}</a></td>
+<td>{{.IP}}</td>
+<td>{{.Body}}</td>
+<td><a href="/_gm/games/{{.GameID}}">game</a></td>
+</tr>
+{{else}}
+<tr><td colspan="6"><span class="note">no messages</span></td></tr>
+{{end}}
+</tbody>
+</table>
+<nav class="pager">
+{{if .Pager.HasPrev}}<a href="/_gm/messages?{{.FilterQuery}}&amp;page={{.Pager.PrevPage}}">&laquo; prev</a>{{end}}
+<span>page {{.Pager.Page}} · {{.Pager.Total}} total</span>
+{{if .Pager.HasNext}}<a href="/_gm/messages?{{.FilterQuery}}&amp;page={{.Pager.NextPage}}">next &raquo;</a>{{end}}
+</nav>
+{{end}}
+{{- end}}

backend/internal/adminconsole/templates/pages/user_detail.gohtml

@@ -1,7 +1,7 @@
 {{define "content" -}}
 {{with .Data}}
 <h1>{{.DisplayName}}</h1>
-<nav class="subnav"><a href="/_gm/users">&laquo; users</a></nav>
+<nav class="subnav"><a href="/_gm/users">&laquo; users</a> · <a href="/_gm/messages?user={{.ID}}">messages</a></nav>
 <div class="cards">
 <section class="panel"><h2>Account</h2>
 <ul class="kv">