feat(admin): plan statistics + node restart/close-ae actions

Final legacy-admin items:
- identity GET /v1/admin/plan-statistics (active/total users + revenue per plan
  from user_plans); surfaced as a breakdown table in /admin/stats
- NodesTable: wire Restart + Close-AE actions (backend already supported them) via
  new proxy routes; was only drain/release before

Full DivineGateWeb legacy-admin parity achieved.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/identity/FlatRender.IdentitySvc/Application/Services/AdminService.cs

@@ -57,6 +57,23 @@ public class AdminService(IdentityDbContext db)
             pays.Sum(p => p.AmountMinor), payingAllTime, daily);
     }
 
+    // ── Plan statistics ──────────────────────────────────────────────────────
+
+    public async Task<List<PlanStatRow>> GetPlanStatisticsAsync(Guid tenantId)
+    {
+        var now = DateTime.UtcNow;
+        return await db.UserPlans
+            .Where(p => p.TenantId == tenantId)
+            .GroupBy(p => p.PlanName)
+            .Select(g => new PlanStatRow(
+                g.Key,
+                g.Count(),
+                g.Count(x => x.ExpiresAt > now && x.CancelledAt == null),
+                g.Sum(x => x.PriceMinorPaid)))
+            .OrderByDescending(r => r.RevenueMinor)
+            .ToListAsync();
+    }
+
     // ── CRM notes / tags ────────────────────────────────────────────────────
 
     public async Task<UserCrmResponse> GetUserCrmAsync(Guid userId)