fix(payment): resolve PR audit issues

- Add payment navigation to AppSidebar (user orders + admin payment menu group with collapse)
- Add 5 missing nav i18n keys (myOrders, orderManagement, paymentDashboard, paymentConfig, paymentPlans)
- Renumber payment migrations 090-100 → 092-102 to avoid conflict with upstream 090/091
- Remove non-payment sora_client_enabled change, restore upstream purchase_subscription fields
- Remove extra 'data' from SettingsTab type union

backend/migrations/094_removed_payment_channels.sql

@@ -0,0 +1,4 @@
+-- Migration 092: payment_channels table was removed before release.
+-- This file is a no-op placeholder to maintain migration numbering continuity.
+-- The payment system now uses the existing channels table (migration 081).
+SELECT 1;