chore(deps): upgrade all dependencies to latest stable

Bring backend and frontend to the latest stable releases (no pre-releases),
including major upgrades that required code migration. Both projects pass
typecheck and production builds.

Backend
- NestJS 10 -> 11 (common/core/platform-express/jwt/passport/bull/cli/
  schematics/testing), @nestjs/config 3->4, @nestjs/swagger 7->11,
  @nestjs/typeorm 10->11
- @kubernetes/client-node 0.21 -> 1.4: migrate ~200+ call sites across 6
  services to the v1 single-object argument API, unwrapped responses, err.code,
  setHeaderOptions for patch content-type, applyToHTTPSOptions. Add regression
  spec k8s-client-v1-migration.spec.ts.
- typeorm 0.3 -> 1.0: relations/select string arrays -> object form
- uuid 9->14 (drops @types/uuid), multer 1->2, bcrypt 5->6, helmet 7->8,
  class-validator 0.14->0.15
- TypeScript 5->6, ESLint 8->9, @typescript-eslint 6->8, jest 29->30,
  @types/node 20->24; tsconfig: strictPropertyInitialization:false,
  ignoreDeprecations, rootDir, explicit types[]
- @nestjs/config 4: jwt.strategy uses getOrThrow; @types/express kept at 4
  (Nest 11 runs Express 4)

Frontend
- React 18->19, Next 14->16 (async params via official codemod),
  Tailwind 3->4 (@tailwindcss/postcss, @import + @config, inline custom @apply),
  framer-motion 11->12, zustand 4->5, three 0.169->0.184, @react-three/* majors
- TypeScript 5->6 (tsconfig target es5->ES2017), ESLint 8->9,
  eslint-config-next 14->16

Infra/docs
- Dockerfiles node:20-alpine -> node:24-alpine (require-esm for k8s client)
- Add UPGRADE.md / UPGRADE.en.md; refresh README tech-stack versions

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

backend/src/billing/billing.service.ts

@@ -161,7 +161,7 @@ export class BillingService {
     const wallet = await this.getOrCreateWallet(userId);
     return this.txRepo.find({
       where: { walletId: wallet.id },
-      relations: ['invoice'],
+      relations: { invoice: true },
       order: { createdAt: 'DESC' },
       take: limit,
     });
@@ -198,7 +198,7 @@ export class BillingService {
 
   // Admin: get all wallets
   async getAllWallets(): Promise<Wallet[]> {
-    return this.walletRepo.find({ relations: ['user'], order: { balance: 'DESC' } });
+    return this.walletRepo.find({ relations: { user: true }, order: { balance: 'DESC' } });
   }
 
   // ─── Invoices ─────────────────────────────────────────────────────
@@ -300,7 +300,7 @@ export class BillingService {
   async getInvoiceForUser(invoiceId: string, user: { id: string; role?: UserRole }): Promise<Invoice> {
     const invoice = await this.invoiceRepo.findOne({
       where: { id: invoiceId },
-      relations: ['user', 'application', 'lines', 'transactions'],
+      relations: { user: true, application: true, lines: true, transactions: true },
       order: { lines: { createdAt: 'ASC' }, transactions: { createdAt: 'DESC' } },
     });
     if (!invoice) throw new NotFoundException('Invoice not found');