feat: add source_provider mapping for actual VPS provisioning

- Update PricingWithProvider type with source_provider and source_region_code
- Update getPricingWithProvider query to JOIN instance_types for actual plan_id
- Use source_provider (linode/vultr) instead of provider_name (Anvil)
- Use source_region_code for actual provider region (ap-northeast, nrt, icn)

Mapping: anvil_regions.source_provider + anvil_pricing.source_instance_id
         → instance_types.instance_id (actual Linode/Vultr plan)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/services/provisioning-service.ts

@@ -196,21 +196,21 @@ export class ProvisioningService {
       return;
     }
 
-    // Get provider
-    const provider = this.getProvider(pricing.provider_name.toLowerCase() as VPSProvider);
+    // Get provider (use source_provider: linode/vultr)
+    const provider = this.getProvider(pricing.source_provider);
     if (!provider) {
-      console.error(`[ProvisioningService] Provider not configured for order ${order_id}`);
-      await this.repo.rollbackOrder(order_id, user_id, order.price_paid, 'Provider not configured');
+      console.error(`[ProvisioningService] Provider ${pricing.source_provider} not configured for order ${order_id}`);
+      await this.repo.rollbackOrder(order_id, user_id, order.price_paid, `Provider ${pricing.source_provider} not configured`);
       return;
     }
 
     // Get OS image ID
     const osImageId = provider.getOsImageId(image);
 
-    // Call provider API
+    // Call provider API (use source_region_code for actual provider region)
     const createResult = await provider.createServer({
       plan: pricing.instance_id,
-      region: pricing.region_code,
+      region: pricing.source_region_code,
       osImage: osImageId,
       label: label || `order-${order_id}`,
       rootPassword: root_password,