feat(deploy): configurable CPU/RAM/disk for app databases

Let users size the database workload from the deploy wizard the same way
Redis/RabbitMQ are configured: a resource card (CPU request/limit, memory
request/limit, storage) on the Resources step, stored in
optionalServiceResources.database.

- entity/DTO: add `database` to optionalServiceResources
- k8s: resolveDatabaseResources() applies user-selected resources on both
  the Helm and K8s-API deploy paths (was hardcoded 100m/256Mi→500m/512Mi)
- billing: bill database CPU/RAM as a separate line on top of the app's
  resources; merge it through the upgrade path too
- wizard: db resource card on the Resources step, disk moved into the card,
  cost preview + review summary include the database resources

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

frontend/src/lib/optional-service-defaults.ts

@@ -7,6 +7,13 @@ import type {
 export type OptionalServiceKey = keyof OptionalServiceResourcesMap;
 
 const FALLBACK_OPTIONAL_RESOURCES: Record<OptionalServiceKey, OptionalServiceResourceConfig> = {
+  database: {
+    cpuRequest: '100m',
+    cpuLimit: '500m',
+    memoryRequest: '256Mi',
+    memoryLimit: '512Mi',
+    storageGi: 1,
+  },
   redis: {
     cpuRequest: '50m',
     cpuLimit: '200m',