feat(chat): unread read-receipts with lobby/game dot and history-open ack

Persist per-message read state as a chat_messages.unread_seats bitmask
(migration 00008): a text message seeds every recipient seat's bit, a nudge
only the awaited seat's. A seat's bit clears when the player opens the move
history or chat (POST /games/:id/chat/read, sent only when something is
unread), and a nudge additionally clears when its recipient answers by moving
(a wired game NudgeClearer, dependency-inverted so game keeps off social).

UI shows a per-viewer unread dot in the lobby (next to the opponent) and the
game score bar — the unread_chat game-view flag seeds it from authoritative
REST views, live chat/nudge events raise it. Opening the move history counts
as reading (even without entering chat): the 💬 fade-blinks twice and the
client acks. Admin Messages gains an unread-only filter, a read/unread column,
and a per-message card with the per-seat read breakdown. Observability:
chat_read_duration histogram + chat_unread_messages gauge + social tracing.

backend/internal/adminconsole/render_test.go

@@ -35,7 +35,8 @@ func TestRendererRendersEveryPage(t *testing.T) {
 		{"games", GamesView{Items: []GameRow{{ID: "g-open", Variant: "scrabble_en", Status: "open"}}, Status: "open", Pager: NewPager(1, 50, 1)}, "?status=open"},
 		{"game_detail", GameDetailView{ID: "g1", Variant: "scrabble_en", 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"},
+		{"messages", MessagesView{Items: []MessageRow{{ID: "m1", SenderID: "a1", SenderName: "Kaya", Source: "telegram", Body: "good luck", GameID: "g1", Unread: true}}, UnreadOnly: true, Pager: NewPager(1, 50, 1)}, "unread only"},
+		{"chatmessage", ChatMessageDetailView{ID: "m1", GameID: "g1", SenderID: "a1", SenderName: "Kaya", Source: "telegram", Kind: "message", Body: "good luck", Unread: true, Seats: []ChatSeatStatusRow{{Seat: 0, AccountID: "a1", DisplayName: "Kaya", Role: "sender"}, {Seat: 1, AccountID: "b2", DisplayName: "Opp", Role: "unread"}}}, "Read by seat"},
 		{"feedback", FeedbackView{Items: []FeedbackRow{{ID: "f1", AccountID: "a1", SenderName: "Kaya", Source: "telegram", Channel: "web", HasAttachment: true, Replied: true}}, Status: "unread", Pager: NewPager(1, 50, 1)}, "replied"},
 		{"feedback_detail", FeedbackDetailView{ID: "f1", AccountID: "a1", SenderName: "Kaya", Channel: "telegram", InterfaceLanguage: "en", BotLanguage: "ru", Body: "please fix the board", HasAttachment: true, AttachmentName: "shot.png", IsImage: true, Banned: true}, "bot: ru"},
 		{"complaint_detail", ComplaintDetailView{ID: "c1", Word: "qi", Variant: "scrabble_en"}, "Resolve"},

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

@@ -0,0 +1,28 @@
+{{define "content" -}}
+{{with .Data}}
+<h1>Message</h1>
+<nav class="subnav"><a href="/_gm/messages">&laquo; messages</a> · <a href="/_gm/games/{{.GameID}}">game</a> · <a href="/_gm/messages?game={{.GameID}}">game messages</a></nav>
+<section class="panel"><h2>Summary</h2>
+<ul class="kv">
+<li><b>Time</b> {{.CreatedAt}}</li>
+<li><b>Sender</b> <a href="/_gm/users/{{.SenderID}}">{{.SenderName}}</a> ({{.Source}})</li>
+<li><b>IP</b> {{.IP}}</li>
+<li><b>Kind</b> {{.Kind}}</li>
+<li><b>Read</b> {{if .Unread}}unread{{else}}read{{end}}</li>
+<li><b>Message</b> {{.Body}}</li>
+</ul>
+</section>
+<section class="panel"><h2>Read by seat</h2>
+<table class="list">
+<thead><tr><th>Seat</th><th>Player</th><th>Status</th></tr></thead>
+<tbody>
+{{range .Seats}}
+<tr><td>{{.Seat}}</td><td><a href="/_gm/users/{{.AccountID}}">{{if .DisplayName}}{{.DisplayName}}{{else}}{{.AccountID}}{{end}}</a></td><td>{{if eq .Role "read"}}<span class="ok">read</span>{{else if eq .Role "unread"}}unread{{else}}sender{{end}}</td></tr>
+{{else}}
+<tr><td colspan="3"><span class="note">no seats</span></td></tr>
+{{end}}
+</tbody>
+</table>
+</section>
+{{end}}
+{{- end}}

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

@@ -6,6 +6,7 @@
 {{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 (* ?)">
+<label class="check"><input type="checkbox" name="unread" value="1"{{if .UnreadOnly}} checked{{end}}> unread only</label>
 <button type="submit">Filter</button>
 <a class="export" href="/_gm/messages.csv?{{.FilterQuery}}">Export CSV ↓</a>
 </form>
@@ -13,19 +14,20 @@
 <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>
+<thead><tr><th>Time</th><th>Source</th><th>Sender</th><th>IP</th><th>Message</th><th>Read</th><th>Game</th></tr></thead>
 <tbody>
 {{range .Items}}
 <tr>
-<td>{{.CreatedAt}}</td>
+<td><a href="/_gm/messages/{{.ID}}">{{.CreatedAt}}</a></td>
 <td>{{.Source}}</td>
 <td><a href="/_gm/users/{{.SenderID}}">{{.SenderName}}</a></td>
 <td>{{.IP}}</td>
 <td>{{.Body}}</td>
+<td>{{if .Unread}}unread{{else}}read{{end}}</td>
 <td><a href="/_gm/games/{{.GameID}}">game</a></td>
 </tr>
 {{else}}
-<tr><td colspan="6"><span class="note">no messages</span></td></tr>
+<tr><td colspan="7"><span class="note">no messages</span></td></tr>
 {{end}}
 </tbody>
 </table>

backend/internal/adminconsole/views.go

@@ -94,11 +94,13 @@ type MessagesView struct {
 	ExtMask     string
 	GameID      string
 	UserID      string
+	UnreadOnly  bool
 	FilterQuery template.URL
 }
 
 // MessageRow is one chat message in the moderation list: its sender (linked to the user
-// card), source, IP, body, game (linked to the game card) and time.
+// card), source, IP, body, game (linked to the game card), time, and whether it is still
+// unread by at least one recipient.
 type MessageRow struct {
 	ID         string
 	SenderID   string
@@ -108,6 +110,32 @@ type MessageRow struct {
 	Body       string
 	GameID     string
 	CreatedAt  string
+	Unread     bool
+}
+
+// ChatMessageDetailView is one chat message with its per-seat read breakdown, for the
+// console message card.
+type ChatMessageDetailView struct {
+	ID         string
+	GameID     string
+	SenderID   string
+	SenderName string
+	Source     string
+	Kind       string
+	Body       string
+	IP         string
+	CreatedAt  string
+	Unread     bool
+	Seats      []ChatSeatStatusRow
+}
+
+// ChatSeatStatusRow is one seat's read status on the message card: the seat index, the
+// occupant (linked to the user card) and its role ("sender", "read" or "unread").
+type ChatSeatStatusRow struct {
+	Seat        int
+	AccountID   string
+	DisplayName string
+	Role        string
 }
 
 // UserDetailView is one account with its stats, identities and recent games.