feat: AI-game refinements (GCG, your_turn, admin, metrics)

Follow-ups on the honest-AI game, same PR:
- GCG export labels the robot seat "AI" instead of its pool name (ExportGCG
  overrides via accounts.IsRobot); the in-app 🤖 is unchanged.
- vs_ai games emit no your_turn (the robot replies instantly, so it would be
  redundant); opponent_moved still advances the UI.
- Admin console shows the AI flag: a 🤖 column in /games and an "AI game" line
  on the game card (GameRow/GameDetailView gain VsAI).
- games_started_total / games_abandoned_total gain a vs_ai attribute; the
  Grafana Game-domain dashboard splits started/abandoned into human and AI
  panels.

Tests: metrics unit (vs_ai split); integration (no your_turn, GCG "AI").

backend/internal/adminconsole/views.go

@@ -192,6 +192,8 @@ type GameRow struct {
 	Status    string
 	Players   int
 	UpdatedAt string
+	// VsAI marks an honest-AI game (rendered as 🤖 in the list's AI column).
+	VsAI bool
 }
 
 // GamesView is the paginated games list, optionally filtered by status.
@@ -214,7 +216,9 @@ type GameDetailView struct {
 	CreatedAt   string
 	UpdatedAt   string
 	FinishedAt  string
-	Seats       []SeatRow
+	// VsAI marks an honest-AI game (shown as a 🤖 flag in the summary).
+	VsAI  bool
+	Seats []SeatRow
 	// HasRobot is true when any seat is a robot, gating the robot-target caption;
 	// RobotTargetPct is the configured global play-to-win rate, in percent.
 	HasRobot       bool