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/096_payment_provider_instances.sql

@@ -0,0 +1,15 @@
+CREATE TABLE IF NOT EXISTS payment_provider_instances (
+    id BIGSERIAL PRIMARY KEY,
+    provider_key VARCHAR(30) NOT NULL,
+    name VARCHAR(100) NOT NULL DEFAULT '',
+    config TEXT NOT NULL,
+    supported_types VARCHAR(200) NOT NULL DEFAULT '',
+    enabled BOOLEAN NOT NULL DEFAULT TRUE,
+    sort_order INT NOT NULL DEFAULT 0,
+    limits TEXT NOT NULL DEFAULT '',
+    refund_enabled BOOLEAN NOT NULL DEFAULT FALSE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+CREATE INDEX IF NOT EXISTS idx_payment_provider_instances_provider_key ON payment_provider_instances(provider_key);
+CREATE INDEX IF NOT EXISTS idx_payment_provider_instances_enabled ON payment_provider_instances(enabled);