feat(landing,billing): public pricing, global discount, services bar & estimator

Backend
- Add platform-wide global discount (platform_settings: global_discount_percent),
  applied centrally in PricingCatalogService.computeTotalsFromDb so it reaches
  every real charge (previews, deploys, renewals, upgrades, invoices). Admin
  GET/PATCH /billing/settings/global-discount.
- Add unauthenticated PublicPricingController (catalog + calculate) for the
  public landing page, returning gross/net and the discount percentage.
- Bill application replicas by the user-selected footprint: app CPU/RAM/storage
  now all scale by replica count; the single-replica database stays unscaled.

Frontend
- Landing: Services bar (PaaS active, DBaaS, KaaS/LaaS "coming soon" with
  expandable runtime/database menus), transparent Pricing section (per-resource
  rate cards with cycle toggle + discount strikethrough), and a cost Estimator
  ("estimate your package").
- Optional services and the database are priced like runtimes: the estimator
  lets users pick their CPU/RAM/storage (and DB type) so the cost scales by need.
- Admin billing: global-discount editor.
- i18n: fa/en strings for services, pricing, estimator and global discount.

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

backend/src/billing/pricing-catalog.service.spec.ts

@@ -5,6 +5,7 @@ import { PricingRate } from './entities/pricing-rate.entity';
 import { AddonRate } from './entities/addon-rate.entity';
 import { OptionalServiceProfile } from './entities/optional-service-profile.entity';
 import { OptionalServiceRate } from './entities/optional-service-rate.entity';
+import { PlatformSetting } from './entities/platform-setting.entity';
 import {
   AppRuntime,
   BillingCycle,
@@ -47,6 +48,13 @@ describe('PricingCatalogService', () => {
     create: jest.fn().mockImplementation((x) => x),
   };
 
+  const settingsRepo = {
+    find: jest.fn().mockResolvedValue([]),
+    findOne: jest.fn().mockResolvedValue(null),
+    save: jest.fn().mockImplementation((x) => Promise.resolve(x)),
+    create: jest.fn().mockImplementation((x) => x),
+  };
+
   beforeEach(async () => {
     jest.clearAllMocks();
     const module: TestingModule = await Test.createTestingModule({
@@ -56,6 +64,7 @@ describe('PricingCatalogService', () => {
         { provide: getRepositoryToken(AddonRate), useValue: addonRepo },
         { provide: getRepositoryToken(OptionalServiceProfile), useValue: optionalProfileRepo },
         { provide: getRepositoryToken(OptionalServiceRate), useValue: optionalRateRepo },
+        { provide: getRepositoryToken(PlatformSetting), useValue: settingsRepo },
       ],
     }).compile();