fix: zero expired codex windows in backend, use /usage API as single frontend data source

backend/internal/service/account_usage_service.go

@@ -1042,6 +1042,11 @@ func buildCodexUsageProgressFromExtra(extra map[string]any, window string, now t
 		}
 	}
 
+	// 窗口已过期（resetAt 在 now 之前）→ 额度已重置，归零
+	if progress.ResetsAt != nil && !now.Before(*progress.ResetsAt) {
+		progress.Utilization = 0
+	}
+
 	return progress
 }
 

backend/internal/service/account_usage_service_test.go

@@ -148,3 +148,54 @@ func TestAccountUsageService_PersistOpenAICodexProbeSnapshotSetsRateLimit(t *tes
 		t.Fatal("waiting for codex probe rate limit persistence timed out")
 	}
 }
+
+func TestBuildCodexUsageProgressFromExtra_ZerosExpiredWindow(t *testing.T) {
+	t.Parallel()
+	now := time.Date(2026, 3, 16, 12, 0, 0, 0, time.UTC)
+
+	t.Run("expired 5h window zeroes utilization", func(t *testing.T) {
+		extra := map[string]any{
+			"codex_5h_used_percent": 42.0,
+			"codex_5h_reset_at":     "2026-03-16T10:00:00Z", // 2h ago
+		}
+		progress := buildCodexUsageProgressFromExtra(extra, "5h", now)
+		if progress == nil {
+			t.Fatal("expected non-nil progress")
+		}
+		if progress.Utilization != 0 {
+			t.Fatalf("expected Utilization=0 for expired window, got %v", progress.Utilization)
+		}
+		if progress.RemainingSeconds != 0 {
+			t.Fatalf("expected RemainingSeconds=0, got %v", progress.RemainingSeconds)
+		}
+	})
+
+	t.Run("active 5h window keeps utilization", func(t *testing.T) {
+		resetAt := now.Add(2 * time.Hour).Format(time.RFC3339)
+		extra := map[string]any{
+			"codex_5h_used_percent": 42.0,
+			"codex_5h_reset_at":     resetAt,
+		}
+		progress := buildCodexUsageProgressFromExtra(extra, "5h", now)
+		if progress == nil {
+			t.Fatal("expected non-nil progress")
+		}
+		if progress.Utilization != 42.0 {
+			t.Fatalf("expected Utilization=42, got %v", progress.Utilization)
+		}
+	})
+
+	t.Run("expired 7d window zeroes utilization", func(t *testing.T) {
+		extra := map[string]any{
+			"codex_7d_used_percent": 88.0,
+			"codex_7d_reset_at":     "2026-03-15T00:00:00Z", // yesterday
+		}
+		progress := buildCodexUsageProgressFromExtra(extra, "7d", now)
+		if progress == nil {
+			t.Fatal("expected non-nil progress")
+		}
+		if progress.Utilization != 0 {
+			t.Fatalf("expected Utilization=0 for expired 7d window, got %v", progress.Utilization)
+		}
+	})
+}