feat: add ESLint flat config, Prettier, dependency-cruiser, and Husky

Setup code quality tooling for the monorepo:
- ESLint 9 flat config with TypeScript, import ordering, and NestJS rules
- Prettier with consistent formatting across all files
- dependency-cruiser enforcing module boundary rules (no cross-module internals, no circular deps)
- Husky + lint-staged for pre-commit hooks
- Auto-fixed existing files for type imports and import ordering

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/app.module.ts

@@ -1,9 +1,10 @@
+import { SharedModule } from '@modules/shared';
 import { Module } from '@nestjs/common';
 import { CqrsModule } from '@nestjs/cqrs';
 import { AppController } from './app.controller';
 
 @Module({
-  imports: [CqrsModule.forRoot()],
+  imports: [CqrsModule.forRoot(), SharedModule],
   controllers: [AppController],
 })
 export class AppModule {}