feat: complete Phase 1 foundation scaffold

- Monorepo: Turborepo + pnpm workspaces with 7 apps/packages
- Backend: NestJS scaffold with 9 modules (auth, tenant, curriculum, simulation, portfolio, ai-coach, analytics, classroom, gamification)
- Frontend: React 18 + Vite + TailwindCSS + shadcn/ui with 10 pages, 14 UI primitives, 3 Zustand stores
- Database: Prisma schema with 19 models, 13 enums, seed script, multi-tenant ready
- Docker: Dev, production, and Portainer Compose files with Traefik reverse proxy
- Configuration: .env.example (47 vars), Zod validation, frontend-safe env exposure
- i18n: English + Greek locale files (10 files), ICU MessageFormat, react-i18next
- Shared packages: @investplay/types, @investplay/ui, @investplay/i18n, @investplay/utils
- CI/CD: GitHub Actions (lint, typecheck, test, build, deploy, PR checks)
- Documentation: CONTEXT.md, ARCHITECTURE.md (10 Mermaid diagrams), API.md, LOCALIZATION.md, DEVELOPMENT-ROADMAP.md
- Infrastructure: Dockerfiles (dev + prod), nginx configs, backup/healthcheck scripts
- Security: JWT auth guards, role-based access, rate limiting, Helmet, CORS, PII sanitization

apps/api/src/modules/tenant/tenant.middleware.ts

@@ -0,0 +1,32 @@
+import { Injectable, NestMiddleware, Logger } from "@nestjs/common";
+import type { Request, Response, NextFunction } from "express";
+
+@Injectable()
+export class TenantMiddleware implements NestMiddleware {
+  private readonly logger = new Logger(TenantMiddleware.name);
+
+  use(req: Request, _res: Response, next: NextFunction) {
+    const tenantId =
+      req.headers["x-tenant-id"] as string | undefined ??
+      req.user?.tenantId ??
+      this.extractFromSubdomain(req);
+
+    if (tenantId) {
+      (req as Request & { tenantId: string }).tenantId = tenantId;
+    }
+
+    next();
+  }
+
+  private extractFromSubdomain(req: Request): string | undefined {
+    const host = req.headers.host;
+    if (!host) return undefined;
+
+    const parts = host.split(".");
+    if (parts.length >= 3) {
+      return parts[0];
+    }
+
+    return undefined;
+  }
+}